Create community page and basic layout

* Add responsiveness, text styling, first pass layout
* Scope border-bottom on h1's to .main class
* Clean up references to global nav partial
* replace border bottoms with HRs, WIP
* Refactor class naming system
* Style hr tags
* Separate styling for community preview on landing page from community page
* Update responsive styling for forum section of community page
* Style logo section
* Add logo section as a partial
* Change `container` class to `wrap-container`

https://trello.com/c/lgtX08mv
![middleman-community-page](https://cloud.githubusercontent.com/assets/5547897/5039957/52de0950-6b5b-11e4-8e86-676cc4063ae9.png)


If we have a `mixins/` folder under `stylesheets`, I might move the styles for `button-style` to there.