Fix some format comparisons
Test doctests in .rst documentation
Fix doctests
Fix doctests on Python 3.2
Fix doctests on Python 2.6
Fix test on Python 2.7
Handle differences in Numpy dtype strings.
Add CHANGES entry.
Merge pull request #18 from mhvk/units-fruit-correction

Units fruit correction
Merge pull request #1715 from mdboom/unit/low-hanging-fruit

Low hanging optimizations in units and coordinates
Merge pull request #1771 from mdboom/docs/doctest-pytest

Run doctests in .rst files
Add dex, dB units; skip tests for mag,dB.decompose() for CDS, VOUNIT
since these do not know dex
Avoid clash between dB and decibyte=dbyte=dB
Add equivalency for logarithmic -> dimensionless, plus tests
Allow complex scale -- for (mag**0.5).decompose()