Update Jython travis build

[c-mita]

The travis instructions for how to run the tests under Jython need periodic updating as fixes/changes are made to the Scisoft nd wrappers we use in place of numpy.

This may prove to be something of a headache as I suspect it won't be a straight-forward "update the version numbers" change. It is nonetheless important, as we depend on this functionality within GDA.

(Pressure SciSoft to provide a proper isolated nd-array package we can use?)