Removed VOtable test
Moved check for <tr> tags to HTMLInputter, removed old test
Modify HTML multi-col test file to be more stressing
Change multi-col handling to leave vals as strings for TableOutputter
Add a table row with a string but no data elements
Simplify logic for selecting table rows
Fix to set blank data values as missing
Add test of informative error if table id not found (currently failing)
Add sanity-check tests of column name handling
Remove unused imports
Added pytest markings to new HTML tests
Made error message more informative for 'table not found'
Restored check for whether id is supplied in identify_table for tests
Fixed expected behavior in test
Altered test for string representation of error
Fixed problem in test with unicode/ascii difference
Deep copying of htmldict, made call in HTMLOutputter more idiomatic
Merge pull request #2199 from larrybradley/2dgauss-covmatrix

Fixed Gaussian2D model when a cov_matrix is input
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.