enh: add travis testing file
Merge remote-tracking branch 'upstream/master' into enh/travis

* upstream/master:
  Added JSON test filed from ProvToolbox and unification tests All the ProvToolbox's JSON was generated by the version https://github.com/trungdong/ProvToolbox/commit/bf13da78a5cdc409571fc9cbe9454597e4dd31fc with the dictionary-related files removed. Unification test cases are taken from https://dvcs.w3.org/hg/prov/raw-file/default/testcases/process.html (only 9 at the moment)
fix: updated dateutil name
fix: added python versions to tests
fix: support for 2.6 set
fix: more set fixes
fix: added support for asserts to unittest
fix: added assertLess
fix: remove checking for py3k
fix: remove redundant ls
doc: fixed docstring for assertLess
Merge pull request #48 from satra/enh/travis

Excellent. Thanks a lot for this, @satra. This will be really useful.