Add rake test description

No behavior change
Simplify code in AS json encoder
Changed update_record to use prepared statements.
Remove valid_type? method

It was supposed to be removed by the preceding two reversions but I did
them in the wrong order.
Removed an old require of an MD5 digest which is no longer used.
copy-edits RDoc in fba496f

This revision makes the terminology uniform with the rest of the file.
In general we describe these methods in terms of the adapter, rather
than the database. (As a side note, if we wanted to refer to the
database we would write "PostgreSQL".)
Merge pull request #9307 from wangjohn/remove_unneeded_md5_digest

Removed an old require of an MD5 digest which is no longer used.
Add CHANGELOG entry for 41ff6a10216f48f43605a1f9cd6094765cab750f

[ci skip]
add tests for ActiveRecord::Base#create
Merge pull request #9312 from Takehiro-Adachi/add_tests_for_ar_create

Add test for ActiveRecord::Base#create
Return false on toggle on error pages
Merge pull request #9313 from bkzl/return-false-on-toggle-on-error-pages

Return false in toggle function on error pages
Gist URLs are now namespaced

see: https://github.com/blog/1406-namespaced-gists
Bump up minitest dependency and remove our own reinvented version of ParallelEach
Document changes in #7968
Merge pull request #9317 from balexand/patch-1

Document changes from #7968 in Upgrading Guide
Add headings to rake routes table
Merge pull request #9318 from steveklabnik/router_headings

Add headings to rake routes table
Add message when you have no routes defined.

Print a message in both `rake routes` and at GET "/rails/info/routes"
that lets you know you have no routes defined, as well as linking to the
Rails Guide on the topic.
Merge pull request #9316 from steveklabnik/no_routes

Print message on stderr when no routes are defined.