added improvements to readme file

The initial intent for this pull request was to add support for Cygwin and advanced install options like pip, but on thinking about it further I realized what a rabbit hole that would be to go down so instead I decided to leave it to the advanced users and clean up a few things I thought needed a spit shine. 

- The major changes are the explicit mention of it only supporting python 2.7 (try and run it on 3+ and it crashes and burns reeeeeeal bad, yet its not explicitly mentioned anywhere). 
- Clarify that the pre-reqs are for USB support. 
- Add test case for post install (run basic_test.py)
- integrate the pre-install dependencies and the installation into one section (personal preference)