support installation via PyPI

[lczub]

TestLink-API-Python-client should be installable from PyPI

[PYTHON27]\Scripts\virtualenv [PYENV]\testlink
[PYENV]\testlink\Scripts\activate
pip install TestLink-API-Python-client

conditions are described in PyPI Tutorial

• extend setup.py (categories, long description, package name)
• extract Installation, Usage and Testing sections out of Readme.md into separate new doc/*.rst files
• divide unit test directory into two directories, one for tests with TestLink interaction, other for standalone tests
• transform readme.md into readme.rst
• create changes.rst files

[lczub]

installation via PyPI is now prepared. First upload to PyPI will be done for the final v0.4.6 release