sprockets 2.9.x doesn't work with uglifier 2.0 yet.

See https://travis-ci.org/rails/rails/jobs/6110543#L1285 for the failure

cc @josh
Fix markdown formatting
Merge pull request #10120 from vipulnsward/change_merge_on_new_hash

change some more merge to merge! on new hashes
Merge pull request #10121 from Agis-/patch-2

Fix markdown formatting
Forgot to lock the uglifier version in our Gemfile

Related with 575838795019f7402992e3bfa83a0c5048cf143d
Merge pull request #10101 from wangjohn/refactoring_routing_mapper

Refactoring some reused code into a method (inside of the routes mapper)
Added a table of html status symols
Added documentation to the FormBuilder class, should help
clarify issue #10115. Also made the field_helpers an explicit list of
methods.
Added a bang to the end of +raise_nested_attributes_record_not_found+
method to signify an exception possibly being raised.
Merge pull request #10123 from wangjohn/added_bang_to_raise_nested_attributes_method

Added a bang to the raise_nested_attributes_record_not_found method
Getting Started Guide: add missing PATCH
each to each_value; remove unused vars
Merge pull request #10127 from vipulnsward/each_to_each_value

each to each_value; remove unused vars
Avoid iterating over records hash when not necessary

If the reflection scope is not flagged with distinct value, there is no
need to iterate over the records, so we avoid that by doing the check
before iterating rather than inside the iteration block.
Here was a 404 error: Active Record Validations

Active Record Validations and Callbacks's URL and name is changed.
Minor AR changelog improvements [ci skip]
Remove unecessary variable call, `#sort!` always returns an array
Remove unused block parameters
Merge pull request #134 from igas/master

Add missing PATCH in Getting Started Guide
Add TEST_DIRS enviroment for constrain test directories in rakefile