Added .gitignore

Signed-off-by: Ika Belerma <ika.belerma@gmail.com>
Testing the waters.

Basically added the all important ExcelLibrary class including a functional
robot test to check the integration between them. BTW: testing this on RF 2.8.4 on Python 2.7.5.

Signed-off-by: Ika Belerma <ika.belerma@gmail.com>