Improvements to Quick-Start Guide

- Add label to Equipment Needed section
- Better copywriting for the intro
- Improve install sections
- Make OS-specific dependency instructions subsections of Dependencies
- Better instructions for getting the source code
- Better wording for Running Freeseer section
- Remove markdown formatting and simplify wording in the last few sections
Merge pull request #12 from Freeseer/improve-quickstart

Improvements to Quick-Start Guide