Update PR template and contributing guidelines (#1574)

.github/PULL_REQUEST_TEMPLATE.md

@@ -34,9 +34,8 @@ Your PR description goes here.
 -->
 
 - [ ] I've followed the [contributing guidelines][contributing-guidelines]
-- [ ] I've added references to all holidays information sources used in this PR
-- [ ] The code style looks good: `make pre-commit` command generates no changes
-- [ ] All tests pass locally: `make test`, `make tox` (we strongly encourage adding tests to your code)
+- [ ] I've run `make pre-commit`, it didn't generate any changes
+- [ ] I've run `make test`, all tests passed locally
 
 <!--
   Thanks again for your contribution!

CONTRIBUTING.rst

@@ -16,10 +16,11 @@ Basics
 
 When contributing with fixes and new features, please start forking/branching
 from the `beta branch`_ to work on the latest code and reduce merging issues.
-
-Contributed PRs_ are required to include valid test coverage **(the goal is
-100% coverage)** in order to be merged. Please don't hesitate to ask for
-help if you'read struggling with tests.
+If you add/change holiday official dates or names you must include references to
+all sources (government sites, archived web pages, wiki pages, etc) you've used
+while working on this PR. Contributed PRs_ are required to include valid test
+coverage in order to be merged. Please don't hesitate to ask for help if you
+need one with the tests.
 
 Thanks a lot for your support.