Feature/site v2

First pass at updating the site with new features and less opinion. Not yet complete, but it's close enough to give a starting point.

Changes (in no particular order):
- updated gems
- updated site to use a simpler format with more links to the style guide
- updated the existing documentation for a better style guide
- prism bower was giving me problems, so i just put the js in the app
- hk logo
- better use of sprockets...
- a more concise directory structure
- placeholders EVERYWHERE
- MOST sass variables have been moved to _variables.css.scss and documented
- `.truncated` class in typogrphy
- removed unnecessary padding variables
- included OPTIONAL and mostly experimental flexbox and flex list styles
- `.centered` class
- media object styles and documentation
- DRYer
- bugs pulled out of several places
- more?