Update README.md

Add troubleshooting section, include a solution for
default browser not launching.

More info on the issue here:
http://stackoverflow.com/questions/5916270/pythons-webbrowser-launches-ie-instead-of-default-on-windows-7
http://docs.python.org/2/library/webbrowser.html
Merge pull request #3 from asfaltboy/patch-1

add troubleshooting section to README.md