Comparisons of Time and TimeDelta
Add tests, if only to avoid the silly bug of the previous commit
Don't cause an exception during configuration file building if matplotlib is installed, but not Sphinx.
Simplify class comparison in tai_difference
Simplified creating new models #980
WIP
Squashed commits implementing format argument, sans io/connect.py update

* 95592e1 Fix multiple registration problem for aliased formats
* 0889189 Redo the auto I/O registration in a more consistent way
* 178a2e4 Add table showing available ASCII I/O connector formats
* 331a69f Add auto-registration of readers/writers  (PARTIAL)
* d0841b1 Add format keyword to ascii.read and write methods
Update io.ascii.connect to provide functions for generic reader registration
Fix mistake in setting global FORMAT_CLASSES
Move info about IPAC position keyword into docstring
Using ascii. instead of ascii: to prefix ascii subformats
Shorten _description for fixedwidth_two_line slightly
Define AAStex io_registry_suffix to be '' to prevent .tex suffix from Latex
Rework table/io docs to reflect new ascii register scheme
Add tests of read/write with format arg
Refactor docs to remove redundancy and use format arg everywhere
WIP
Fix python 2.6 incompatibility in test_write
Fix doc ref mistake and provide additional refs for read/write params
Fixed the points discussed in #1203