Conversions to SkyCoordinates should use astropy machinery for ICRS->GCRS conversion - #1

Angular diameter distance for positive curvature (astropy#4723)

The axis argument was added in astropy#3792 and is passed correctly to sigma_clip, but
then mean, median and std did not use axis and were computed on the whole array.
This commit changes this to use axis to compute the statistics.

Also another minor annoyance is that, with Numpy 1.10, np.ma.median always
return a MaskedArray, even when axis is None. This was not the case in previous
version (and will probably be fixed in the future), and mean and std return
a scalar. So if it happens here, we take the first element of the array.

 Fix sigma_clipped_stats to use the axis argument

Allow using a tuple of keys in Table.sort

Update equivalencies.py

…y powers.

Also fixes a problem with lists as input to ufuncs.

Ensure that scaled dimensionless quantities can be raised to arbitrary powers.

fixed wrong rendered changelog entry and contributor name [skip ci]

Fixed indentation problem with author name

…rPower_fix

Allow base with dimensionless quantity as base for np.power.

added bayesian information criterion and akaike information criterion

Compatibility code for Numpy 1.7 wasn't removed, so keep it for now.

Ref astropy#2824 an older bug report. On Python 3 `ResourceWarning` warnings were
raised because the FITS convenience methods (`getdata`, `getheader`, `append`,
`update`) were not closing files as they were supposed to.

Remove unnecessary sort when defining __all__

…d expose publically available bodies

…was used for earth and solar system body

…scalar times