[JRO] Display category(-ies) for topics
[JRO] Rm attachments and translate `t:img` tags to image tags

The current way where we add attachments to a post via the nested attributes -- posts having many attachments, etc -- is a poor method of adding images to posts. As a result the app should allow external methods of doing this. In my mind this should be another engine handling file uploads and displaying it.

So - this commit is the first step to removing these. Instead of completely removing attachments for now we'll leave them in there and will, instead, translate all `[t:img]` tags to real image tags (in markdown or bbcode)

* Remove `accepts_nested_attributes_for :attachments` from Post.
* Add a rake task -- `thredded:update_legacy_timg_tags` -- to make the translation in each post.
* Add two traits for post - `:markdown` and `:bbcode`
* Remove the attached image filter
* Remove attached files form fields
* Remove ability to attach images via email
[JRO] BREAKING NEWS: I am an idiot.

Until now there were people not getting @ mention notifications because they had not updated their profile / settings. This commit will create a default and will send them their @ notification if so.

* Swap double negative for something more human
* use `first_or_create` instead of the `try` to ensure a record exists - either a default record or a previously set one.
* Derp.
[JRO] Release notes for 0.0.13
Bump to 0.0.13
[JRO] Update rails dependency

To allow for 4.0.x AND 4.1.x the `~>` needs to be changed to `>=`. This
is in prep for the 4.1 release in a month
[JRO] Update gem dependencies

* Update rails dependency to be GTE 4.0.0 instead of ~> (in prep or 4.1)
* Update other gems
* Delete helpers not being used
[JRO] Create a base mailer class

The thredded resque mailer gem can now hook into this one class instead
of two different classes (post, topic)
[JRO] Add rubocop.yml

Clean up a few things while working w/nested form branch
[JRO] Replace nested forms with form objects

accepts_nested_attributes for is a poor solution to the nested objects in forms problem so replacing that functionality, along with the nested_form gem, is a must.

* Add app/forms directory and autoload it
* Remove nested_form
* Replace all instances of nested_form_for with form_for
* Tighten up the permissions for strong params being used
* Remove accepts_nested_attributes_for in the topic model
* Add NewTopic and PrivateTopic form objects
* Remove nested attributes from setup controller
* Delete form partial that's only used once.

Misc:

* Standardize form object naming as `form` and not `f`
* Remove `multipart: true` html options for the forms
* Remove unnecessary `.topic_form` class on form tags
* Chill with the nested partials

Rename NewTopic -> TopicForm
[JRO] Fix breaking topics#edit form

`category_options` was being called on a Topic object, and the method
doesn't exist. But decorating the topic, and adding the method to the
decorator fixes it.

Also add correct, and uniform, css classes to the div wrapping around
the topic edit form.
[JRO] Format code and fix ordering issue in spec

* Some fixes to the formatting in this file while I'm in here (thx
  rubocop!)
* A spec down below was setting the cofniguration on the Thredded
  singleton and wasn't cleaning up after itself. Therefore, depending on
  the order of the tests being run, it would bleed over into subsequent
  tests and cause failure. This commit resets `Thredded.user_path` after
  it is changed
[JRO] Little form cleanup

* Update div wrapper class
* Nest form inside UL
* No need for the url options
[JRO] Remove unused "state" column on topics
[JRO] Make sure posts inherit messageboard filter

Somehow this was a regression
Link to user from post on topic page

Simply turns the name into a link.
Merge pull request #27 from taylorkearns/link-to-user

Link to user from post on topic page
[WIP] Start splitting apart thredded_topics

* Create a thredded_private_topics table
* Change Thredded::PrivateTopic to subclass from AR::Base instead
* Start filling in the blanks on the dependencies - posts, decorators, etc
* Add associations, copy over code from Thredded::Topic to
  Thredded::PrivateTopic
[JRO] Fix more specs
[JRO] Create new table and copy data over