Adding notes on PATCH to the upgrade guide.

Discusses compatibility between PATCH and PUT, as well as how to add
support for JSON PATCH to your application.

Fixes #10439.
stop swallowing exceptions in assert_queries.  Methods that raise an
exception are unlikely to pass this assertion, but since the assertions
raise an exception, the original exception is lost.
Don't autorequire mocha to avoid deprecation warnings

- https://travis-ci.org/rails/rails/jobs/7264822 contains deprecated
  warnings given by Mocha version 0.14
- 632f215da added Mocha 0.14 to Gemfile
- But with the version, require: false was removed
- So Mocha started giving deprecation warnings
- Acc.to Mocha documentation(https://github.com/freerange/mocha#bundler)
  it should not be auto required.
Add test to AR's counter_cache_test.rb

According to
https://github.com/rails/rails/blob/b601399b72ab56cc01368f02615af99f45d1
4f02/activerecord/lib/active_record/counter_cache.rb#L14, u can pass
more then one association to the `reset_counters` method.
Fix tests which started to fail due to commit 0123c39f41e2062311b2197e6e230ef8ad67e20e

Due to commit 0123c39f41e2062311b2197e6e230ef8ad67e20e, column
topic.unique_replies_count has been added, and these test started to
fail since the tests depends on the topic tables column info.
Merge pull request #10675 from prathamesh-sonpatki/dont-auto-require-mocha

Don't autorequire mocha to avoid deprecation warnings
Merge pull request #10676 from tkhr/add-test-to-counter_cache_test.rb

Add test to counter cache test.rb
Fxied some typos
Merge pull request #10597 from steveklabnik/patch_documentation

Adding notes on PATCH to the upgrade guide. [ci skip]
Merge pull request #10678 from prathamesh-sonpatki/typos

Fixed some typos