ProbtrackX2 interfaces, fixes #792
added a docstring
ran make specs, this changed several files, but did not generate a test.
Merge remote-tracking branch 'upstream/master' into probtrackx2
ran make specs after python install to generate auto tests
fixed example, added dummy files
added ProbTrackX2 to fsl __init__.py
modified CHANGES to include ENH FSL ProbTrackX2 interface
fix: resolved conflict
Merge pull request #2 from satra/enh/p2

Enh/p2
Merge remote-tracking branch 'origin/pr/831'

Conflicts:
	CHANGES