Remove FireBreath project.
Added initial version of plain NPAPI plugin.

This plugin doesn't yet have any XInput code, and so doesn't actually
function, but it does successfully supply a stubbed API to build upon,
and works in Chrome and Firefox.
Fixed LICENSE.txt and added license header.
Added XInput wrapper. Working in Chrome + Firefox.
Some minor cleaning up.
Update Makefile and README to add Ubuntu info.
Use a refcounter for the thread. Fixes #4.

This seems to allow multiple pages to work now, and cleanup when closed.
Firefox appears to stop receiving events once one tab has been closed
however, but I will open a new bug for that.
Update README (remove reference to old master branch).