Changing FITS table write function to have default value of Nan for float type cols
Changing default value for float columns from 1e20 to Nan in fits table write function
Changing the float comparison for filled value to np.allclose to enable Nan masking for float32 as well. Also added test cases for float64, and float32
Add default config values to FakeApp allowing tests to run without crashing on missing config attributes.
Update test to reflect new expected reults since the changes in 5da52803d2d9dd3a5c2663353899bd04655ab53a
A few miscellanous tweaks to the test runs:
 * Fix an issue where an error could occur when running setup.py test
   with the -P option but there are no Sphinx docs for the selected
   package
 * It turns out running pytest_ignore_collect causes paths to be
   ignore for all of pytest, not just a single plugin.  Kind of a pain,
   that.  This tweaks how DoctestPlus uses pytest_ignore_collect to
   implement the doctest_norecursedirs option.
Fix #2230: Make the progressbar work with the IPython qtconsole.
Add CHANGES entry.
Removing unnecessary comment
Rebuild from fresh master since rebasing was failing horribly.
Extra - got into title for 0.4
Moved ParametricModel._model_to_fit_params to being a static method in Fitter;
this is the first step in separating concerns so that only Fitters are
responsible for getting their inputs into the correct format they need.

This allowed elimitating a lot of code rot in the process.

This did require outright removing a handful of test cases, but those tests
would be better handled within the fitter tests anyways--simply marking some
parameters as constrained should have no bearing on a *model's* behavior by
itself.
First step of splitting up the MatrixRotation2D model, as has been
suggested a number of times.

This changes MatrixRotation2D to simply Rotation2D with a single
parameter: angle (currently given in degrees--Quantity support will
allow some more flexibility here).  Its inverse is to simply apply a
rotation by the same amount in the opposite direction.  Added a simple
test case for this because why not?
Add a new AffineTransformation2D model to replace the functionality of the old MatrixRotation2D where it could take an arbitrary 2D matrix.  This specifically limits the matrix to 2x2 (hence 2D).  This could easily be extended to be n-D but is currently just implementing what might have actually worked with the old MatrixRotation2D, with the addition of an additional 'translation' parameter which takes a translation vector, allowing the full range of affine transformations.  Includes a couple simple tests.
Incorporate @larrybradley's changes from #2266 to ensure that the sense or rotatioin is in fact counter-clockwise
Add changelog entry
Support multiple and divide on angles.
Make these validate methods private for now so that support doesn't need to be maintained for them in case they are changed/removed later.
Actually, per the TODO comment, _validate_angle is entirely superfluous.
Fix documentation and formatting suggestions made by @cdeil