reverse order of operands
improve logic
correct inverse and start a new Travis build.
Update the minimum Numpy version to 1.5.

Remove workarounds and "knownfail" tests for Numpy 1.4.

Add an explicit check for the correct version of Numpy on importing astropy.
Use a substitution for the Numpy version so we don't have to remember to
update it in multiple places.
Remove another Numpy 1.4 workaround
Fix Numpy 1.5 compatibility.
Merge pull request #1487 from eteq/cartesian-to-quantity

Make CartesianPoint and coordinate cartesian accessors Quantities
Merge pull request #1353 from nden/performance-improvement

Performance improvement
503e3ebc inadvertently introduced code that is not compatible with
Python 2.6 (subprocess.check_output).  This remedies that.
Remove extraneous print statement introduced in ba451181
Fix subprocess.check_output on early Python 2.6
Make sure we have an old and working py.test installed, as a temporary measure
Only upgrade numpy -- everything else should use the specified versions.
Merge pull request #1501 from mdboom/downgrade-pytest

Attempt to fix Travis after pytest 2.4.0 upgrade
Make tests compatible with pytest 2.4.0
Split the SIPModel class into forward and inverse model. Corrected inverse of ShiftModel and ScaleModel. Fixed name in parameter lookup.
ensure rotations work with scalar input.
use docstrings from base class
pep8