Working fix for unsigned int conversions
Convert print statement to warning
All uint tests now working
parametrize test and other minor changes
Also parametrize uint image tests
fully parametrize uint tests
Fix different hdu number in compressed files.  Also, closes #362 and closes #880
Disable test of 64-bit compressed image
add placeholder for uint parameter
A bit of formatting cleanup, and also added a test to ensure that uint=False does not result in implicit conversion of column data to unsigned ints (which currently fails).  For now uint will be a boolean value that applies to the entire file, but later we can easily make it more fine-grained.
Seems to get support for the uint parameter basically working on table columns (note the test as I originally wrote it was wrong: With uint=False the bzero parameter still causes the data to be converted to float and rescaled).
Gets the tests fully passing on 64-bit systems.  This was very tricky due in part to what (I think?) is a but in Numpy where adding an int64 to a uint64 causes the result to be recast as a float64 (I think I've heard of a bug like this before elsewhere).  The other issue is that when scaling a 64-bit int with bzero, the resulting float64 lost too much precision to be able to accurately scale back to the original int values.  Rather than consider this an acceptable loss I used float128s for scaling 64-bit ints.
This code was broken to begin with--in a table with multiple columns where one column contains uint data, any columns that did *not* contain uint data would be set to zero.  In any case I think the implementation of scaling for table columns still needs a little more thought; it should work more consistently with images.  Even the non-uint case for scaling table columns is poorly tested at the moment so that needs to be worked on.