Speed up fk4_no_e_fk4 test.
Mention acceptable shortcut for `list(six.iterkeys(d))`
Fix Python 3 issue on big endian platforms
Add CHANGES entry
Fix for #1900
Don't run tests if scipy is not present
Merge pull request #1903 from nden/linear-models-deriv

Fix for #1900
Update CHANGES.rst

Changelog entry for #1900.
Update CHANGES.rst

Ugh, a3616a8089bea8ad05f987f4ae8e7569fc746045 should have referenced #1903.
Fix definition of "bar"
Merge pull request #1910 from mdboom/unit/bar

Definition of units.bar is off by a factor of 1000
Merge pull request #1891 from mdboom/docs/six-guidelines

Additional note to six coding guidelines
Alternative fix for #1908.  Don't display scientific notation in sexagesimal.
Update CHANGES.rst
Fix #1766: Use Table's repr for io.votable.tree.Table
Add a CHANGES entry
It doesn't make to test this for Unicode guidelines.
Merge pull request #1887 from mdboom/testing/python3-endianness

Fix for endianness test on Python
Merge pull request #1883 from mdboom/coordinates/speed-up-fk4-fk4-test

Vectorize test_fk4_no_e_fk4
Fix typo