Test case for issue with global state in obspy.taup.
Reset some variables in taup when loading model.

This allows multiple calls to not trounce each other's data, eventually
resulting in completely incorrect results.

Fixes #728.
Merge pull request #728 from krischer/taup_fix

Calling `obspy.taup.taup.getTravelTimes` repeatedly eventually fails.
Merge branch 'releases'