removed specific mention of 2.7
Added Tkinter based wrapper GUI

No single line of core changed.
Use markdown for commands and paths
Merge pull request #111 from thekarangoel/patch-1

Use markdown for commands and paths
always respect mppl if passed
improved error msg
Merge branch 'master' of https://github.com/dgorissen/coursera-dl
catch the case when sample lectures are present and hidden
remove newline from print
Update README.md

Add one more usage instruction to remove permission problem.
Merge pull request #116 from kctong529/master

Update README.md