Travis integration

TODO: Since I'm not the repository owner, the following things need to be done by repo owner:
1. Read http://docs.travis-ci.com/user/getting-started/ on how authorize Travis CI to access Github account.
2. Push any change to trigger first Travis CI build.
3. Optionally add a status image to README.rst (http://docs.travis-ci.com/user/status-images/) - choose appropriate form from drop down menu on the left.
4. Generate API key for deploying builded apk (http://docs.travis-ci.com/user/deployment/releases/). For this you need to do next things:
      A. Install Ruby on your machine. 
      B. Install Travis command line client (gem install travis). 
      C. Use Travis CI command line client to generate encrypted key for accessing you public repo (travis setup releases). 

For every tagged version Travis will upload apk.