[API docs](http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-phone_field) for `phone_field` provide no information on what the method actually does. no description nor access to source code. so added this

This reverts commit d63b69ba.

framework

Bad Regexp exploits "fix" master branch

prevent users from unknowingly using bad regexps that can compromise security (http://homakov.blogspot.co.uk/2012/05/saferweb-injects-in-various-ruby.html)

This is the last chapter before I go back and make sure the guide is
complete/review

The `path` method on missing helper errors is inconsistent with the
implementation on LoadError in Ruby 2.0.  Wrap up the missing helper
exceptions so that the inconsistent behavior is mirrored in Ruby 2.0
(until we can figure out *why* it's inconsistent).

That change to update_attribute was considered
to be too subtle and was reverted in 30ea9230
just before Rails 3 shipped. Later we introduced
update_column (Rails 3.1).

These lines don't help to mitigate CVE. They only turn [nil] into nil, w...