Build overhaul

Overhaul of the build facilities to make full use of cmake:

- Having a working install on win32 plaftorm;
- Providing a YajlConfig.cmake for easy use of the package through cmake (see the documentation for further information);
- Run tests using [CTest](http://www.cmake.org/cmake/help/v2.8.8/ctest.html);
- Do the packaging using [CPack](http://www.cmake.org/cmake/help/v2.8.8/cpack.html);
- Continuous integration using [Travis CI](https://travis-ci.org/cloderic/yajl).