Added section about London Traffic Tamer Challenge.
Merge pull request #49 from nathorne/addLondonChallenge

Added section about London Traffic Tamer Challenge.
Move VI firmware config tutorial to VI docs.
Update links to android library installation.
Clear up a section header in Android tutorial.
Triage some problems with the tutorial.
Remove stray brace from tutorial.
Switch example to engine speed, easier to test.
Mention deleting exiting android-support-v4.
Re-organize tutorial to start with completed example.
Fix problem with case-sensitive CONTRIBUTORS vs contributors