Upstream biicode

This PR modifies (non-intrusively) the CMakeLists in order to use the www.biicode.com dependency manager.
It also adds a couple of files under the "bii" subfolder.
Included a .travis.yml proposal for initially handling travis-ci builds.

Please check:
- Biicode block: http://www.biicode.com/diego/glfw
- Biicode documentation: http://docs.biicode.com/c++/examples/glfw.html
- Github fork: https://github.com/drodri/glfw
- Travis build: https://travis-ci.org/drodri/glfw
It was not exactly a copy, as it prepended the src/ path to files. Also I did not want to touch the src/CMakeLists.txt, trying to be as less intrusive as possible. 

But as you point out, it can be improved. I have excluded the unnecessary parts of src/CMakeLists.txt with an IF(BIICODE) guard, and include it from the root CMakeLists, then process ${glfw_SOURCES} to get the source files.

The result is indeed shorter and easier to maintain, thanks.