Fix n problems in README and Gem (#52)

* Fix two problems in README

* Update README.md

* Add notice for possible error when upgrading

* Only define Field if using graphql >= 1.8 to avoid a load error

README.md

@@ -11,7 +11,7 @@
 Add this line to your application's Gemfile:
 
 ```ruby
-gem 'graphql-pundit'
+gem 'graphql-pundit', '~> 0.7.0'
 ```
 
 And then execute:
@@ -20,6 +20,15 @@ And then execute:
 $ bundle
 ```
 
+### Upgrade Notice
+
+If you're upgrading from an earlier version, make sure to delete your
+`bootsnap` cache, to avoid a load error (see
+[this issue](https://github.com/ontohub/graphql-pundit/issues/51)).
+The cache files are usually located in the `tmp` directory in your
+repository and are named `bootsnap-compile-cache` and
+`bootsnap-load-path-cache`.
+
 ## Usage
 
 ### Class based API (`graphql-ruby >= 1.8`)
@@ -163,7 +172,7 @@ class User < BaseObject
                         authorize: true,
                         record: ->(obj, args, ctx) { ctx[:current_user] }
   field :password_hash, ... do
-    authorize policy: ->(obj, args, ctx) { ctx[:current_user] }
+    authorize record: ->(obj, args, ctx) { ctx[:current_user] }
   end
 
   # will use AccountPolicy#email? with the first account as the record (the policy was inferred from the record class)
@@ -184,7 +193,9 @@ initialize the policy with, but for mutations there is no parent object.
 ###### `before_scope` and `after_scope`
 
 `before_scope` and `after_scope` can be used to apply Pundit scopes to the
-fields. Both options can be combined freely within one field.
+fields. Both options can be combined freely within one field. The result of
+`before_scope` is passed to the resolver as the "parent object", while the
+result of `after_scope` is returned as the result of the field.
 
 ```ruby
 class User < BaseObject

lib/graphql-pundit/field.rb

@@ -6,10 +6,13 @@
 
 module GraphQL
   module Pundit
-    # Field class that contains authorization and scope behavior
-    class Field < GraphQL::Schema::Field
-      prepend GraphQL::Pundit::Scope
-      prepend GraphQL::Pundit::Authorization
+    if defined?(GraphQL::Schema::Field)
+      # Field class that contains authorization and scope behavior
+      # This only works with graphql >= 1.8.0
+      class Field < GraphQL::Schema::Field
+        prepend GraphQL::Pundit::Scope
+        prepend GraphQL::Pundit::Authorization
+      end
     end
   end
 end

lib/graphql-pundit/version.rb

@@ -2,6 +2,6 @@
 
 module GraphQL
   module Pundit
-    VERSION = '0.7.0'
+    VERSION = '0.7.1'
   end
 end