Code cleaning

I removed the Firefox-addon-sdk, hogan.js and closurelibrary from the third_part directory. Now they are not tracked in github (they are not part of the project, they are requirements now!).

I made a "build.sh" script that installs everything automatically
I think it would make more sense to use git submodules for this. As an added advantage, the folders would be pinned to a specific commit, which would prevent issues when upstream updates their repositories.