Missing an explicit mention to Cython dependency in documentation

[Martin-Floor]

I found that Cython is required for installation but is not mentioned in the list of dependencies. It is included in the apt instructions for Ubuntu users; however, it won't be apparent when using other OS until you bump with an error. Since most dependencies are python-based, generating a precompiled CONDA environment would be great. For example, look at what the PyEmma package does:

http://www.emma-project.org/latest/INSTALL.html