Move scripts code back to .travis.yml file.

.. and remove unused install.sh and script.sh.
coveralls in same dir
Add client tests to travis.yml.
Use $TRAVIS_BUILD_DIR environment variable to cd into backend/frontend.
Disable glclient tests in travis.
Split test and coveralls in different lines.
Install nodejs, and client dependencies (via npm).
Add mocha test (in GLClient) to travis.yml.

* Build a glclient package and move to the default directory as intended by
  glbackend
* Run globaleaks in development mode to prepare tests for mocha
* Run mocha.

Note: GLClient path is automatically discevered with -z option, so we don't need
to tell globaleaks where to look for it..
Maybe it's python-pip to break things.

Python environments in travis are indeed virtualenvs, so we shall:
* install stuff inside virtualenv (no python-pip)
* never use sudo to install with pip
Make clear the separation between frontend and backend in travis scripts.