Removed hardcoded path to slicer. Reverted back to having CLIs in PATH
instead of --launcher.
Merge pull request #520 from chrisfilo/fix/slicer_path

Removed hardcoded path to slicer.
Does not crash if SPM is not installed.
Merge branch 'master' of https://github.com/nipy/nipype.git
doc: clarify nipy slice timing
Merge pull request #555 from satra/fix/nipyrealign

doc: clarify nipy slice timing