Building mash with CMake

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As we discussed at #49 one of the first things to do was using CMake to build Mash. This would let us build the project on other platforms (as Windows) "for free" meanwhile it helps to integrate things like the python API building process.

You can finde the implementation in [the cmake branch in my fork] (https://github.com/jomsdev/Mash/tree/cmake). I will explain all the changes in my pull request but we need a development branch first #51 .

Briefly, the changes have been:

• CMake integration
• .gitignore updated (removing all the Makefile stuff, we do not build the project in the folder anymore)
• INSTALL.txt modified explaining the new building process
• src and include folders created