Make rbslack more buildable.

This change adds a build config, and fixes up some issues in the setup.py file.

Reviewed at https://reviews.reviewboard.org/r/6107/
Overrode TogetherJS default css to make the extension look more like Review Board.

This change adds some CSS to make the TogetherJS UI fit in better with Review
Board's color scheme and design.

Testing Done:
Launch 'Chat' by clicking the Chat tab located on the right side of the header
bar. The following views on any page illustrate the new changes:

- The right TogetherJS menu should be dark and similar to the header bar.
- The pop-up titled "Invite a friend" should mimic containers in the admin
  panel.
- Clicking on the first icon in the TogetherJS menu, the secondary menu that
  pops up mimics the pull down shown the Support tab in the header bar is
  hovered over.
- Clicking the last icon (Chat) or third icon (Audio Chat) in the TogetherJS
  menu, the pop-up should also mimic the containers found in the admin panel.

Reviewed at https://reviews.reviewboard.org/r/6066/
Fix checklist deployments on production sites.

The "Checklist" javascript object was being defined using 'var', but the
minification process sticks everything inside of a function. As a result, none
of this was accessible from the global namespace.

Trivial fix.
Fix up some basic style issues in the checklist python code.

This change renames "checklistResource.py" to "resources.py" and fixes up some
trivial python issues.

Testing done: Ran pep-8 tool.
Fix up style of the checklist javascript.

The javascript code in the checklist didn't match a lot of our coding style.
I've cleaned things up a bit. Trivial change.
Restyled notification messages.

This change makes the notification message pop-ups fit in better with Review
Board's visual look.

Testing Done:
1. Launch Review Together in one browsers.
2. Click "Add" button and open the provided URL in another browser. (Note the
   popup in this "Add window")

3. In the second browser, the notification window upon load should look
   similar to the "Add window".
4. Exit the second browser.
5. A pop up in the first browser should have a notification message saying the
   peer has quit. This window will resemble the body of the "Add window".

Reviewed at https://reviews.reviewboard.org/r/6214/
[rbnotefield] Work around a breakage with rendering change entries.

Review Board < 2.0.7 breaks when trying to render changes to the Note
field if adding content for the first time after the review request has
already been published. The old value for the field was 'None', which
broke the rendering due to the expectation of strings.

While Review Board 2.0.7 is getting a fix for this, we still want to
work around it for earlier releases. This adds a new
render_change_entry_html() function that just normalizes the values
before calling the parent function, ensuring we're dealing with empty
strings.

Fixes bug #3549
Reviewed at https://reviews.reviewboard.org/r/6291/
[rbnotefield] Release version 1.0.1.

This version fixes issues with rendering change descriptions for the
note field on versions of Review Board prior to 2.0.7.