docs: update CONTRIBUTING

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

CONTRIBUTING.rdoc

@@ -1,7 +1,7 @@
 = Source Repository
 
-Rake is currently hosted at github. The github web page is
-https://github.com/ruby/rake . The public git clone URL is
+Rake is hosted at GitHub. The GitHub Web page is
+https://github.com/ruby/rake . The public Git clone URL is
 
   https://github.com/ruby/rake.git
 
@@ -12,32 +12,30 @@ If you wish to run the unit and functional tests that come with Rake:
 * +cd+ into the top project directory of rake.
 * Install gem dependency using bundler:
 
-    $ bundle install  # Install bundler, minitest, etc.
+    $ bin/setup  # Install development dependencies
 
 * Run the test suite
 
     $ rake
 
-= Rubocop
+= RuboCop
 
-Rake uses Rubocop to enforce a consistent style on new changes being
-proposed. You can check your code with Rubocop using:
+Rake uses RuboCop to enforce a consistent style on new changes being
+proposed. You can check your code with RuboCop using:
 
-  $ ./bin/rubocop
+  $ bin/rubocop
 
 = Issues and Bug Reports
 
 Feel free to submit commits or feature requests.  If you send a patch,
-remember to update the corresponding unit tests.  In fact, I prefer
-new feature to be submitted in the form of new unit tests.
+remember to update the corresponding unit tests.  In fact, the team prefers
+a new feature to be submitted in the form of new unit tests.
 
 For other information, feel free to ask on the ruby-talk mailing list.
 
-If you have found a bug in rake please try with the latest version of rake
+If you have found a bug in rake, please try with the latest version of rake
 before filing an issue.  Also check History.rdoc for bug fixes that may have
 addressed your issue.
 
-When submitting pull requests please check the rake Travis-CI page for test
-failures:
-
-  https://travis-ci.org/ruby/rake
+When submitting pull requests, please check the status checks on your PR page
+to confirm if it says "All checks have passed".