BF: doctest output difference workarounds

We were getting trivial doctest failures from format differences; see:
http://nipy.bic.berkeley.edu/builders/dipy-bdist32-32/builds/2/steps/shell_4/logs/stdio
Merge pull request #179 from matthew-brett/py3-doctest-fixes

BF: doctest output difference workarounds.
BF: fix python 3 doctest in fvtk

Missed a print statement in the doctest.