Fix issue #22
Add optional Xinerama support

Enable by making with `make XINERAMA=1`
Add Xinerama explanation in the readme
Fix issue LemonBoy/bar#25
Merge pull request #26 from boblehest/master

Fix issue LemonBoy/bar#25
Take BAR_OFFSET into account. Fixes #29.
Merge pull request #1 from LemonBoy/master

Xft support