Added version as command line parameter

Use -v or --version shows the version as in __init__.py
Added version as a command line parameter

Use -v or --version
Update README.rst

Added description for errors related to lxml on python 3.3+
Update README.rst
Added Usage info of -v for version

Also added troubleshooting for windows and python 3.3+ lxml errors.
Added the [-C](clear cache) parameter in the usage info ( it was missing )
Update howdoi.py
Update howdoi.py

Edited to keep it consistent with original style.
Merge pull request #91 from hrishikeshsathe/master

Added version as command line parameter