Add no-heading option to the automodapi sphinx ext

This add the option to not have the auotmodapi extension add a top
level title, i.e `astropy.nddata Module`.
couple of docstring typos
Speed up fk4_no_e_fk4 test.
Better use of __array_finalize__ and __array__ in quantity/longitude
Correct mistakes in use of wraps, views, and instances in CartesianPoint
(viz., __quantity_instance__, __quantity_view__, and __array_wrap__)
Add test cases for Quantity with record-array dtype
Expand comment on making scalars 0-dimensional arrays
Mention acceptable shortcut for `list(six.iterkeys(d))`
Fix Python 3 issue on big endian platforms
Add CHANGES entry
Merge pull request #1848 from mhvk/quantity-improved-array-views

Better use of __array_finalize__ and __array__ in quantity/longitude/CartesianPoints
Updated utils.timer to use modeling, related doc, and tests. Updated conesearch timer to reflect changes in utils.timer. Fixed timing related tests in conesearch.
Moved six import to the top as suggested by @mdboom
do_fit() method now accept any astropy.modeling model and fitter, as suggested by @eteq
Fix for #1900
Merge pull request #792 from taldcroft/table/pickle

Table unpickling fails
add convenience functions age and comoving_volume
Don't run tests if scipy is not present
Fixed do_fit() method documentation as suggested by @eteq
Merge pull request #1896 from pllim/timer-fitter

Updated utils.timer to use modeling, fixed related conesearch tests