Improve the testing guide [ci skip]

Improve the "Testing Rails Applications" guide adding a section for
testing helpers and a little note about associations with ActiveRecord
and YAML fixtures.

Also add a link to Fixture Builder ; yet another replacement for
fixtures such as Machinist or FactoryGirl.
Remove conditional, since results are always an instance of `ActiveRecord::Result`
Updated guides with latest method [ci skip]

for blank?
fixed file name references [ci skip]
Updated guides with latest method [ci skip]
Removed doc of removed method diff [ci skip]
Fix the SQLite gem name
Add packages list for ArchLinux [ci skip]

Add the packages required on Arch Linux when setting up the development
dependencies
Remove $VERBOSE = nil from tasks.rb

Permanently setting $VERBOSE to nil causes unwanted side effects (warnings generated by app code are
silenced when triggered by a rake task but visible otherwise). silence_warnings {} would be safer to
use here since it resets $VERBOSE back to what it was when the block finishes.
Refactor `ArrayParser`

* Constantize parse token
* Remove extra param passed to `parse_data`
grab executable from rubygems

As done here d7fc97d3f90c0e30865d32ce202658f03248cacc
Revert "Fix the SQLite gem name"

This reverts commit 700c6c65bcce17d4c61423ceaef031bcbe203337.

Bot the `sqlite3` and `sqlite3-ruby` gems exist.
https://rubygems.org/gems/sqlite3
https://rubygems.org/gems/sqlite3-ruby

In fact, they both point to the same github repository.
https://github.com/luislavena/sqlite3-ruby

However, the last one hasn't been released since 2011, while the first
one keeps getting regular releases.
Refix my misreading of the diff

sorry @robin850.
Thanks @fxn
Add a SQL example for `not` [ci skip]

To share a certain logic across other examples, let's add a sample SQL
code generated by the given Ruby code
Use hyphenated version of assert_url [ci skip]
Fixes typo in Object#try!
Update Rails 3.2.x guide link [ci skip]
Update of 'The Asset Pipeline' guide for Rails 4. [ci skip]
Merge pull request #11620 from spajus/update_docs

Update Rails 3.2.x guide link [ci skip]
Minor refactor - Uses Enumerable#to_a instead of iterate and add to an
array