Travis ci publish release

It hasn't been easy but I think it was for the best. The Travis-ci build now will run on OSX instead of Linux. This allows to easily use a specific version of Mono, 3.2.3 is configured right now, but it does even allow to specify multiple versions to build in parallel (a matrix in travis speak). 
A custom build of Nant is also part of the script, which allows to run it properly under Mono 3 and seems to solve the never ending problems I always with it.

Once the build is completed a .boo script is run to upload a new *release* asset to GitHub. I've already created a release named [alpha](https://github.com/bamboo/boo/releases/tag/alpha) to push the builds from master. To authenticate **it uses my own token so you will need to provide your own** for it to work by following these instructions:

- Generate a "Personal Access Token" in your profile page in GitHub
- Encrypt the token for travis:
  - cd /path/to/boo
  - gem install travis
  - travis encrypt GITHUB_TOKEN=<the github token>
- Include the output of the travis command in the .travis.yml file under "env: global: secure:"