update to work with django 1.7
update requirements.txt
update test suite
fix requirements.txt
fix imports
enable Travis CI
drop python 2.6 support
bump version number
Merge branch 'release/0.1.5'

* release/0.1.5:
  bump version number
  drop python 2.6 support
  enable Travis CI
  fix imports
  fix requirements.txt
  update test suite
  update requirements.txt
  update to work with django 1.7