Fix argument handling in irsa.Irsa.query_region

* The default spatial query type (spatial='cone') was incorrectly
  capitalized (should be spatial='Cone'), so that using the default
  always caused an empty result set.
* An 'else' clause now catches completely unrecognized spaital query
  types.
* Coordinates are now formatted in a way that is recognized by the Gator
  service.
updated tests to match @lpsinger's changes
Merge pull request #1 from keflavich/fix_irsa

Updated tests
Use explicit field name in format

This is required in Python 2.6 to avoid the following exception:

    ValueError: zero length field name in format
IRSA partial refactor; changed tests and polygon parsing substantially
Merge branch 'keflavich-fix_irsa' into fix_irsa

Conflicts:
	astroquery/irsa/core.py
Merge pull request #160 from lpsinger/fix_irsa

Fix argument handling in irsa.Irsa.query_region