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
TST: workaround for bug in nose --with-doctests overloading sweepargs module over imported decorator

See: https://github.com/nose-devs/nose/issues/92
TST: Run tests (still nonlabile only) via nosetests directly and with --with-doctest
BF: nosetests --with-doctest has problems (probably shortage of tests) with -s
BF: travis - install statsmodels and reportlab for more thorough smoke testing using doctests