Fixes Issue #72 and Issue #39 - Adds support for F keys

Provides support (and test) for the F keys 1-19 as described
on the homepage.

Signed-off-by: ciaranj <ciaranj@gmail.com>
Merge pull request #77 from ciaranj/add_f_key_support

Fixes Issue #72 and Issue #39 - Adds support for F keys