Added some classifiers for PyPI

[ClasherKasten]

I only added classifiers i'm sure they are correct.
Tests show that the library runs on all the listed python versions and on both CPython and PyPy.

Some classifiers i wasn't sure:

• Development Status :: 4 - Beta Looking at this little "article" about Stages of development i'm not sure which of the classifiers should be added
• Environment :: Console I think it is correct, but i don't have to deal with classifiers often. Also there are no explanations about them, so...
• Operating System :: OS Independent Basically this is correct to, because the library tries to be OS independent. But in my opinion it isn't tested enough on Windows.
• Topic :: Terminals or Topic :: Software Development :: Libraries :: Python Modules or both? Not quite sure.
• Intended Audience :: Developers think this is true too, but eventually i just misinterpreted the use of the library

[AnnaSasDev]

I've added:
Environment :: Console , Operating System :: OS Independent, Development Status :: 4 - Beta (as indeed this looks the most logical), Topic :: Terminals