TST: Add tests for nipy_* scripts

We weren't testing the scripts until now.
BF: fix misspelled import of nibabel

The script appears to have been broken for a long time...  Tests are
good.
RF: refactor scripts to extend arguments and help

Add more help and command line arguments. Make tsdiffana work better
without a screen.
NF: setup helper for windows executable scripts

Now we have tests for the scripts, I finally find out that the scripts
weren't executable on Windows using the default install.

Add a distutils hack adapted from Twisted / IPython to make the
installed scripts executable from the Windows command line.
RF: run local script files through Python

On Windows, we can't run the local files through the shell because they
don't have needed ``.bat`` or ``.py`` extension. On Posix, we might have
the wrong Python interpreter named on the first line - for example -
"#!/usr/bin/env python" won't necessarily work for every platform, and
might not be the Python we're interested in.  So, run the scripts
through the interpreter we're running in already, if the scripts are
from the source.
BF: deal with spaces in paths for script arguments

Windows temporary directory names revealed the problem.
BF: check for symlinks looking for local scripts

Common case where we might not have installed the scripts is where we've
symlinked the code directory into the path somewhere; check for that
case.
RF: add debug print for script tests

Debug print tells us which command got run for debugging; we need to
know whether we're picking up the scripts on the path or the ones in the
development directory.
RF: get DEBUG_PRINT from environment

From Yarik's suggestion.
Merge pull request #245 from matthew-brett/test-scripts

Test scripts

We weren't testing the scripts. When I added some tests, I realized that there were a little broken, and that they were completely broken on windows. This pull request adds the tests and fixes to make them pass.