Add ACPI event identifier compatible with Ubuntu 14.04

The ACPI event for rotating the screen in and out of tablet mode has a
slightly different identifier in Ubuntu 14.04 than in 13.10. Add this
identifier to the list of events monitored by spin.
Rewrite README

Rewrite README, and replace the term "stylus proximity monitoring" with "palm
rejection". Update code and GUI to reflect these changes. Also perform
some minor code cleanup here and there.
Enable .gitignore