Bugfix: memo field returned index as string. (Reported by Alex Grönholm)
Added some tests.
Merge pull request #1 from jashort/master

Python 3 compatibility, invalid dates in database (Jason Short)
Bugfix: memo field with all spaces was not returned as None.
Rewrote field type D parser.
Field M parser now checks for len(data) instead of field.length.

This makes is a little bit easier to write tests.
Removed __enter__() / __exit__() from Table. (No longer needed.)
Logical fields with value "?" are now returned as None.
Updated setup.py.
Fixed typo in readme.