Fix many links, implement better link system

 - Fixed links for "Argparse" and "easy_install" in directions sections.
 - Implemented index based link system (less confusing to write).
 - Fixed a few problems which was arising by previous linking system.
Merge pull request #47 from santosh/master

Use more consistent markdown hyperlinking for the README file.

The old way could, potentially, bit us in the future. The new way may be more
cumbersome, but it is safer.