Rename 'index.html' to 'resume.html'

The 'index.html' was renamed to 'resume.html'. This is to better align
with future pages that are created (i.e. home.html, contact.html, etc.).
Also, a symbolic link was created for the 'index.html' file which points
to 'resume.html'. Until more work is done, the landing page of the site
will be the resume page.

Signed-off-by: Prakash Surya <me@prakashsurya.com>
Rename 'index.css' to 'main.css'

The 'index.css' file was renamed to 'main.css'. This was motivated by
the fact that there is no longer a "real" index.html file. This CSS file
contains generic styling each page needs to have, styling specific to a
HTML pages should be named accordingly (i.e. resume.html -> resume.css,
contact.html -> contact.css, etc.).

Signed-off-by: Prakash Surya <me@prakashsurya.com>