MUMUP-1402: Collapsible Sidebar

Youtube-esque collapsible sidebar. The sidebar is shown by default, since it I don't think it would be smart to relegate the navigation for the sight to a small menu icon by default. 

Still need to add the ability to remember whether sidebar is open or closed per user. I believe that's on the uPortal side though?

### Notable tweaks:
- Mobile menu now has this black and white image of campus instead of the crest
- Quick links added to the sidebar as a concept for how this could look. I am personally a huge fan of this approach, but I know Phyllis had reservations about it.
- Marketplace icon is a star. Cog icon didn't really make sense to me.
- When sidebar is minimized, the width of the main content is col-sm-11, rather than col-sm-10. Hurray for more real estate!

I took some liberties with the style, let me know if you have any thoughts/concerns/suggestions for them.

### Screenshots:
![image](https://cloud.githubusercontent.com/assets/1919535/5480671/03ac913a-860e-11e4-92f6-13a6fb0ac515.png)

![image](https://cloud.githubusercontent.com/assets/1919535/5480683/1c93eafe-860e-11e4-8f2d-69a83bcdab8b.png)

![image](https://cloud.githubusercontent.com/assets/1919535/5480687/2cb2b1cc-860e-11e4-876b-b592e03189fe.png)

![image](https://cloud.githubusercontent.com/assets/1919535/5481366/c90f2e40-8615-11e4-9a44-7b5ac6f96e54.png)


You generally want all media queries all in one place rather than scattered throughout the css, though I could see putting them at the bottom of every less file. There's no hit performance-wise. I talked to Joe and April and they recommended leaving it like this, if that works for y'all. Perhaps we can reevaluate if this responsive.less file gets out of hand in the future, and pull out styles into the bottom of their respective files.