Add 'color.js' MathJax extesion (fix #3)

The following section on Wikipedia should render properly now:
http://en.wikipedia.org/wiki/Extended_Kalman_filter#Discrete-time_predict_and_update_equations
Add manifest_version (v2)

See http://developer.chrome.com/extensions/manifestVersion.html for details
Update .gitignore
Prepare to release v0.0.5