Py3 csv fixes

More detailed testing revealed a subtle error in csv file handling for Python 3 and windows.  The errors are the first and second errors here:

http://nipy.bic.berkeley.edu/builders/nipy-bdist32-32/builds/4/steps/shell_4/logs/stdio

It turned out that csv files need to be opened in different modes on python 2 and 3.  Make a compatibility wrapper for that and work round it in one example where that might be an issue.