Add Sass possibilities.

[bl0bmaster]

With this PR the above code add 1 16px icons 1 64px and 1 256px icons

<link rel="stylesheet" href="jam.css" />
<i jam-16 arrows-h></i><i jam-64 anchor></i><i jam-256 _500></i>

This PR modify:

• the SVG to delete width="24" height="24" values in all SVG's.

This PR add :

• a Makefile
• a sass file