Improved signature generation script by adding avatar support. Improved
the README file.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	README.md
	sig.php
Removed unneeded indents that were conflicting, and readded image header,
along with browser image output (rather than saving image file).
Merge pull request #1 from jis2507/master

Added avatar support to signature image generation. Improved README