Added short descriptions of the sample Flask LIT Provider project files.
Control flow diagram of how edX works with LTI.
Reference to Flask tutorial.
Modified the Flask control flow diagram
Modified the Flask control flow diagram
Modified Heroku parameters
Changed link to github.com/mitodl/mit-lti-flask-sample
made the terminal commands 'copy-and-paste' as recommended.
Rewrote QuickStart commands to allow copy-paste operation, on Carson's suggestion
Removed call to run.sh script