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
Merge tag '0.1.5' into develop

0.1.5

* tag '0.1.5':
  bump version number