Add Travis configuration file
Add Travis configuration file

Travic-CI allows us to do automatic tests when pushing to repos
like our Github repo. This helps us maintain compatibility with
different versions of python and helps us do regression testing
to make sure we don't unintentionally lose any features.

okfn/datapackage-model-py,okfn/datapackage-py,sirex/datapackage-py,sirex/datapackage-py,datapackages/datapackage-py,okfn/datapackage-model-py,datapackages/datapackage-py,okfn/datapackage-py