revamp sidebar heading and link colors

Old style: greigh headings and red links

![old](https://cloud.githubusercontent.com/assets/2289/4821440/c23333ce-5f2c-11e4-9c2e-b82c38c79d3e.png)

New style: red headings and (darker than text) greigh links, red on hover

![new](https://cloud.githubusercontent.com/assets/2289/4821444/df33f9cc-5f2c-11e4-8118-952a69a6d2e7.png)

I think this new style makes the different sections (package info, keywords, dependencies) easier to distinguish, and less bold red text on the page seems like a good thing. What does @rockbot think?