Update gems.

As described in step 1.2 of
http://guides.rubyonrails.org/3_2_release_notes.html.
Rails to latest 3.2 - 3.2.15
Add default Rails 3.2 development settings.

As suggested in http://guides.rubyonrails.org/3_2_release_notes.html
Disambiguate File from ActiveRecord::Fixture::File
Don't specify format in template name.

In render calls, that's now deprecated in favour of using the :formats
option.
Highlighter is now an option.

Passing it as an argument is deprecated.
In excerpt, radius is now an option.

Passing it as an argument is deprecated.
Remove virtual attribute created_at

The need for this was removed in
0ec315c52a731ff149977b9231a15770fa3bd742, and it now causes a
MissingAttribute error.
Use calls to write_attribute

Under the Rails hood, using the setters for attributes now involves
calling the getters too, (for a will_change? check), so these calls
became circular - use write_attribute instead.
Change class for newer version of mail gem.
Mock methods need to call mail() to generate a proper mail.
Remove obsolete patches.
Update method name in patched method.
Remove obsolete test.
Update spec to match upgraded mail gem behaviour.

The new name value doesn't escape a double quote within single quotes,
which seems more correct.
Silence deprecation warnings

The warnings about plugins interfere with incoming mail handling.
Add some dummy exception notification addresses

ActionMailer now checks for a 'to' address on sending mail, so supply
one so that we can check exception notification mail sending.