PEP: values should be compared to None using `is` not `==`

numpy arrays compared this way do an elementwise comparison and in the
future lists/tuples may do the same, using `is` we find out whether the
variable has been set to be None which makes more sense.
FF: previous commit introduced a syntax error in attributetools.py
BF: manifest (for zip files) should include tests/data/*.psyexp
PEP: None should be compared using `is` not `==`

also stripped a lot of whitespace
Merge pull request #699 from peircej/master

PEP: values should be compared to None using `is` not `==`