Print better messages while testing.
Hack to get tests working with vtk on travis.
On more hack for vtk-5.8.

This is dirty but is version specific and seems like a VTK issue
specific to 5.8 that is holding up our tests and is not reproducible on
my Linux VMs running 13.04 and Deepak's 12.04 VM.
Skipping the PLY reader tests since ...

... the reader seems busted with the version of VTK on travis-ci.
Merge pull request #104 from enthought/travis-ci-fixes

Travis-CI error fixes.