Reallow comparison with 0 even for dimensional quantities
And also treat inf and nan as quantities that can have arbitrary units
Ensure coordinates.tests.test_distance does not fail
Document _can_have_arbitrary units and apply to all members; add extra test
Preparing release 0.3b1
Back to development: 0.3
Fix rst doctests in modeling
Fix rst doctests in coordinates
Fix rst doctests in convolution
Merge pull request #1743 from mdboom/doctest/modeling-2

Fix rst doctests in modeling (again)
Merge pull request #1746 from mdboom/doctest/coordinates-2

Fix rst doctests in coordinates
Merge pull request #1254 from mhvk/units-zero-always-ok

Quantities should always allow comparison with zero
Fix Python 3.x syntax error.
Merge pull request #1747 from mdboom/doctest/convolution-2

Fix rst doctests in convolution
Initial refactoring on modeling index page
Add a Trapezoid fit to the 1D example
Added sentence describing the fitting
Fix model names
Don't use repr to format the version string in the setup.py. If the release is done with Python 2 and the version string is unicode this makes the setup.py invalid in Python 3 by prepending the 'u' for unicode literals.  Don't want to use encode either, however, since if someone makes the release using Python 3 that will lead to making the version a bytes literal which we don't want either.
Merge pull request #1473 from astrofrog/modeling/improve-getting-started

Simplify/clean up 'Getting started' section for astropy.modeling