Code and structural changes to facilitate packaging and distribution

[Evolution0]

Made the required changes to facilitate packaging and binary distribution + other minor tweaks.

Setup files have been created and requirements updated, readme has been converted to ReStructuredText to support PyPI and the other Markdown files converted for consistency.

Happypanda now uses AppDirs for proper version level appdata directories when using the new --home option, this directory is contained in: X:/Users/USER/AppData/local/Pewpews/Happypanda/VERSION/

Small tweaks included in this PR in addition to the packaging changes (but still relevant):

• Taskbar icon will now properly display in Windows.
• The downloads directory will now also be put in X:/Users/USER/AppData/local/Pewpews/Happypanda/VERSION/ when using --home
• Imports cleaned up.

[Evolution0]

Hold off on merging, I'd like all tests to pass properly and some issues with them seemed to have popped up.

[rachmadaniHaryono]

• why renaming version/executors.py to version/executors.py not detected on git?
• maybe keep pep8 formatting later?
• icon/taskbar icon is not shown. see gitter
• style.css is not loaded see error below. the screenshot is at gitter
• pytest also doesn't recommend use __init__.py http://doc.pytest.org/en/latest/goodpractices.html

style.css error:

QIODevice::read (QFile, "/home/myusername/Downloads/some_folder/happypanda/happypanda/app_constants.py/res/style.css"): device not open

e: add pytest and __init__.py