Admin styles

[gemfarmer]

What this PR does:

• A first step towards transforming the look and feel of the Forecast Admin
• Uses colors, styles, fonts that are consistent with the Forecast public facing application
• Slight modification to default django admin

@stvnrlly Ready for review!

What still needs to be done:

• Reconfigure django admin templates to allow the main content view on the / of the admin to be used as an admin-wide navigation. The breadcrumb is currently a placeholder for this, but can be removed once this navigation is put into place. I didn't do this for the first iteration because it involved considerable restructuring. With the styles in place, it shouldn't be terribly difficult to keep the same look with a reconfigured navigation strategy

*EDIT: more on reconfiguration:

@stvnrlly: Sure. I left it a little vague, I guess. The reconfiguration I was referring was making the left column on the mock above an admin wide navigation panel. That currently isn’t possible because app_list, the object that generates it isn’t permitted on every admin view. According to @jacobian this involves extending AdminSite with a custom each_context() method.
Because of this layer of difficulty, I decided to work with the default functionality until I have more bandwidth or someone who understands django better than myself can help me put that in place.

[stvnrlly]

🎆

[gemfarmer]

💥 Thanks again @stvnrlly !