dependencies: bumped Whoosh to veriosn 2.7.4. Fixes #4283

dependencies: bumped Markdown library to 2.6.7

dependencies: bumped mako templates to 1.0.6

dependencies: bumped waitress version to 1.0.1

dependencies: bumped supervisor to 3.3.1 version.

dependencies: bumped gevent to 1.1.2 and greenlet to 0.4.10 versions.

dependencies: bumped msgpack to version 0.4.8.

dependencies: dropped obsolete Dulwich library.

requirements: re-organized requirements.txt file.

dependencies: organized test requirements. - introduced requirements_test.txt file to store test requirements. - add parsing into setup.py of requirement files and passing it automatically.