Corrects tox targets
Corrects tox targets

Issues:
Fixes #838

Problem:
The tox targets did not include python 2.7 and included a version of
BIG-IP that did not xist (11.5.1)

Analysis:
This patch correct the bigip version and adds python 2.7 support

Tests:

F5Networks/f5-common-python,F5Networks/f5-common-python