Added some description to generate actionview gem [ci skip]
don't convert mailer default values to procs

Invoke mailer defaults as procs only if they are procs, do not convert
with to_proc.  That an object is convertible to a proc does not mean it's
meant to be always used as a proc.  Fixes #11533
Updated guides with latest method [ci skip]

for blank?
text_area should handle nil value option like text_field
fixed file name references [ci skip]
Updated guides with latest method [ci skip]
Removed doc of removed method diff [ci skip]
Simplify select_one method.

The select_all method always returns ActiveRecord::Result instance,
and the ActiveRecord::Result includes Enumerable mixin.
If #empty?, #first method returns nil. Thus we can simplify this method.
Fix indentation.
Fix the SQLite gem name
Merge pull request #11570 from joelcogen/harmonize_text_field_and_area

text_area should handle nil value option like text_field
Merge pull request #11579 from kennyj/refactor_20130724

Simplify select_one method.
Add packages list for ArchLinux [ci skip]

Add the packages required on Arch Linux when setting up the development
dependencies
Merge pull request #11559 from bughit/11533_to_proc

don't convert mailer default values to procs
rake -> bin/rake
AM Guide: Should be "different formats".
Cleanup task for informing about hstore
Merge pull request #11584 from Peeja/actionmailer-guide-typo

ActionMailer Guide: Should be "different formats".
Merge pull request #11585 from vipulnsward/hstore_change

Cleanup task for informing about hstore
Allow overriding of all headers from passed environment hash

Allow REMOTE_ADDR, HTTP_HOST and HTTP_USER_AGENT to be overridden from
the environment passed into `ActionDispatch::TestRequest.new`.

Fixes #11590