Tweak home page styles. Use pink for links.

I made some tweaks to home page styles—mostly spacing adjustments and small character-adds. I also set the default <a> color to the pink used in the help section. Finally, I added an editor image (with a clean color scheme) to accompany the "Try it." section.

#### Before
![before](https://cloud.githubusercontent.com/assets/2092395/3504526/db3f5eb6-0648-11e4-9531-5565df1e1bff.png)

#### After
![after](https://cloud.githubusercontent.com/assets/2092395/3504527/e1a20eac-0648-11e4-88b3-fe221537d0d7.png)