Lower the SQLAlchemy requirement version (#206)
Lower the SQLAlchemy requirement version (#206)

This version will ensure compatibility with more CKAN versions, as older
than the current one are stuck with SA 0.9.6.

All tests pass when using 0.9.6 and I have reviewed the code looking for
potential backward incompatible things, without finding anything.
datapackages/tabulator-py,okfn/tabulator-py,frictionlessdata/tabulator-py,okfn/datatable-py,frictionlessdata/tabulator-py