add testing code for ASTs

[lea-hagen]

There isn't currently any testing of the AST code. Tests should be added. This should include adding an optional input to the AST code that assigns a particular random seed.

[s-goldman]

created the files but within the make_ast_input_list.py file, gridf = h5py.File(sedgrid_fname) is still getting the wrong filename

[karllark]

@s-goldman : is this issue ready for closing based on #286?

[s-goldman]

I added testing to a couple of the files, but I think there is more testing to be done.

[karllark]

Ok. Will assign to v2.0.

[cmurray-astro]

~~I'll work on this for hack day~~ (update: did not make progress! this is still wide open!)