Updated Display.py with pressed feature enabled

It is with reference to issue no 120
https://github.com/ingenuitas/SimpleCV/issues/120
Added exception raising if linux user does not have permission to work with camera
Fixes typo from commit which fixed typos

Fixes typo in #399
Merge pull request #388 from alekzvik/linux_camera_perms

Added IOError raising if linux user is not in 'video' or 'sudo' group. Thanks this should save a few people's problems.
Merge pull request #385 from atul2512/ML-module1

Updated Display.py with pressed feature enabled
Merge pull request #402 from victsou/develop

Fixes typo from commit which fixed typos
Merge branch 'develop' of github.com:ingenuitas/SimpleCV into develop