Support v8 of the API (#55)

* Change API version to be v8.

* Add user_settings manager and relevant API commands.

* Update projects and items API.

* Update and refactor all tests.

* Re-add force_history in item complete.

* Add forgotten projects.move() method.

* Update items.update_date_complete() to accept a "due" parameter.

* Add changelog between v7 and v8.

* Move changes to changelog and change format a bit.

* Remove deprecated "message" parameter

Ref: #44

* Fix wrong call methon in uploads.py

Ref: #52

* Include somehow missed changes to changelog file.

CHANGELOG.md

@@ -0,0 +1,79 @@
+# Changelog
+
+## [8.0] - 2019-04-18
+
+* All arguments expecting a date/time must be formatted according to [RFC
+  3339](https://tools.ietf.org/html/rfc3339), and all return values are also
+  using the same format.
+* The `item_order` and `indent` properties of projects, that denoted a visual
+  hierarchy for the projects (the order of all the projects and the level of
+  indent of each one of them), were replaced by `parent_id` and `child_order`,
+  which denote a real hierarchy (the parent project of a project and the order
+  of all children of a specific parent project).
+* The `projects.add()` method now expects a `parent_id` and `child_order`
+  parameter, instead of the `item_order` and `indent` parameters.
+* The `projects.update()` method doesn't expect an `item_order` and `indent`
+  parameters anymore, but it doesn't accept the new `parent_id` and
+  `child_order` parameters as well, as the way to change the hierarchy is now
+  different (see the `projects.move()` and `projects.reorder()` methods).
+* The new `projects.move()` method must be used to move a project to become
+  the child of another project or become a root project.
+* The new `projects.reorder()` method must be used to reorder projects in
+  relation to their siblings with the same parent.
+* The `projects.delete()` method now expects only an `id` parameter, instead
+  of the `ids` parameter, and it deletes the project and all the projects's
+  descendants.
+* The `projects.archive()` method now expects the `id` parameter, instead of
+  the `ids` parameter, and it archives the project and all the project's
+  descendants.
+* The `projects.uncomplete()` method now expects an `id` parameter, instead
+  of the `ids` parameter, and it restores the project as a root project.
+* The `projects.update_orders_indents()` method was removed.
+* The `date_string`, `date_lang`, `due_date_utc` properties of items were
+  replaced by the `due` object.
+* The `item_order` and `indent` properties of items, that denoted a visual
+  hierarchy for the items (the order of all the items and the level of indent
+  of each one of them), were replaced by `parent_id` and `child_order`, which
+  denote a real hierarchy (the parent item of an item and the order of all
+  children of a specific parent item).
+* The `items.add()` method now expects a `parent_id` and `child_order`
+  parameter, instead of the `item_order` and `indent` parameters.
+* The `items.add()` and `items.update()` methods now expect a `due` parameter,
+  instead of the `date_string`, `date_lang` and/or `due_date_utc` parameters.
+* The `items.update()` method doesn't expect an `item_order` and `indent`
+  parameters anymore, but it doesn't accept the new `parent_id` and
+  `child_order` parameters as well, as the way to change the hierarchy is now
+  different (see `item_move` and `item_reorder`).
+* The `items.move()` method does not accept the `project_items` and
+  `to_project` parameters, but a new set of parameters specifically `id`, and
+  one of `project_id` or `parent_id`.  Another difference stemming from this is
+  that only a single item can be moved at a time, and also that in order to
+  move an item to become the child of another parent (or become a root level
+  item) the `item_move` command must be used as well.
+* The `items.update_orders_indents()` method was removed.
+* The new `items.reorder()` method must be used to reorder items in relation
+  to their siblings with the same parent.
+* The `items.delete` method now expects only an `id` parameter, instead of
+  the `ids` parameter, and it deletes the item and all the item's descendants.
+* The `items.complete()` method now expects the `id` parameter, instead of
+  the `ids` parameter, and it completes the item and all the item's
+  descendants.  In addition the new `date_completed` parameter can also be
+  specified.
+* The `items.uncomplete()` method now expects an `id` parameter, instead of
+  the `ids` parameter, and it uncompletes all the item's ancestors.
+* The new `items.archive()` method can be used to move an item to history.
+* The new `items.unarchive()` method can be used to move an item out of
+  history.
+* The `items.update_date_complete()` method now expects a `due` parameter,
+  instead of `new_date_utc`, `date_string` and/or `is_forward` parameters.
+* The possible color values of filters changed from `0-12` to `30-49`.
+* The `date_string`, `date_lang`, `due_date_utc` properties of reminders were
+  replaced by the `due` object.
+* The `reminders.add()` and `reminders.update()` methods now expect a `due`
+  parameter, instead of the `date_string`, `date_lang` and/or `due_date_utc`
+  parameters.
+* The state now includes an additional new resource type called
+  `user_settings`.
+* The user object now includes the `days_off` property.
+* The `since` and `until` parameters of the `activity/get` method are
+  deprecated, and are replaced by the new `page` parameter.