Attempt to fix #1179.  Test failing on Debian/MIPS because of an errant floating point warning
Units now allow complex values
Upgrade to six 1.4
Rename UnitsException to UnitsError.
Move some tests related to equivalencies from test_units to test_equivalencies
Add missing import
Fix import
Fix #1005: Don't allow strings as values in quantities
Merge pull request #1179 from mdboom/votable/mips-failure

votable/tests/vo_test.py failure on Python 3.3.2
Merge pull request #1400 from mdboom/misc/upgrade-six

Upgrade six to 1.4
Merge pull request #1338 from mdboom/unit/move-equivalencies-tests

Move some tests related to equivalencies from test_units to test_equivalencies
Merge pull request #1005 from mdboom/unit/disallow-string-quantities

Quantity behavior strange with strings as values
Merge pull request #1384 from alexrudy/complex-quantity

Complex Quantities, conversion, and dimensionless quantities
Merge pull request #1406 from mdboom/unit/rename-exception

Rename UnitsException to UnitsError
Treat scales as unity if they are offset from unity at machine precision
Only apply the is_effectively_unity check when assigning the ._scale internal attribute, making it unncessary to use whenever comparing .scale to 1.  This still places onus developers of the units package to remember this check whenever updating ._scale, but that's less trouble than the current case.