Small bug fixes, patch up the units in wcs and a error in mapcube
animator
Fix a small annotation bug in MapCubeAnimator

Also split out the creation of the axes into a seperate method
so it can be overloaded
Fixed the examples for sunpy.map
improved test case for Database.add_many

check if the undo history is really empty after having called this method
added method Database.remove_many

analogous to add_many, this method only saves one entry in the history,
making it possible to undo removing many entries at once.
added method Database.clear_histories
Update lightcurve.rst
Made current wcs tests more in-depth
Merge pull request #918 from derdon/dbstuff

added new Database methods: remove_many and clear_histories
Added examples to WCS docstrings, fixed a couple notes
Added sanity check for converting back from transformations
Fixed typo
Merge pull request #922 from amras1/test-wcs

Added testing for ``sunpy.wcs``
Merge pull request #920 from Hypnus1803/patch-3

Update lightcurve.rst
Removed the references to the old .show method
Merge pull request #911 from Cadair/bug_fixes

Various bug fixes.
Merge pull request #916 from dpshelio/mapdoc_fix

Fixed the examples for sunpy.map