Allows for logging to a file.

Other than logging information to the standard output, also log messages
to a file (robottelo.log).
Fixed role tests
fixed usergroup tests
Merge pull request #285 from sghai/fix-test

Fixed failed tests( roles and usergroups)
tab_primary is now a common locator
Merge pull request #286 from kbidarkar/fix-primary-tab

tab_primary is now a common locator
Merge pull request #288 from omaciel/log-to-file

Allows for logging to a file.