BF: add mvpa2.viz to distribution.  Closes #143

Thanks robbisg for the report
ENH: adding shebangs and executable permissions to some examples missing them
BF: guard import of IPython.ipapi with externals.exists (for doctests safe harvesting)
BF: use our warning as the last resort anyone trying to find removed ChannelDataset
DOC: added title parameter
NF: scatter plot between underlay and overlay intensity
BF: make sure that identity transformation works (to show examples of poor alignment)
RF+BK: chance "-o" parameter from overwrite to output directory, to conform to other command line functionality
ENH: raise an error if any command line commands fail. Addresses https://github.com/PyMVPA/PyMVPA/issues/139
Merge pull request #145 from nno/_tent/afni

minor improvements in prep-afni-surf while the whole destiny/future of this submodule is still unclear
BF: Fix wrong intentation
Merge branch 'master' into cmdline_modular

* master:
  BF: Fix wrong intentation
  ENH: raise an error if any command line commands fail. Addresses https://github.com/PyMVPA/PyMVPA/issues/139
  RF+BK: chance "-o" parameter from overwrite to output directory, to conform to other command line functionality
  BF: make sure that identity transformation works (to show examples of poor alignment)
  NF: scatter plot between underlay and overlay intensity
  DOC: added title parameter
  BF: use our warning as the last resort anyone trying to find removed ChannelDataset
  BF: guard import of IPython.ipapi with externals.exists (for doctests safe harvesting)
  ENH: adding shebangs and executable permissions to some examples missing them
  BF: add mvpa2.viz to distribution.  Closes #143