sunpy/sunpy: v0.8.3

This is a quite large bug fix release. I want to highlight that we have had many commits from new contributors to SunPy and to thank them for helping with bug fixes! The full changelog is: ~sunpy.net.dataretriever.clients.XRSClient now reports time ranges of files correctly. [#2364] Make parse_time work with datetime64s and pandas series [#2370] CompositeMap axes scaling now uses map spatial units [#2310] Moved license file to root of repository and updated README file [#2326] Fix docstring formatting for net.vso.attrs [#2309]] Fix coloring of ticks under matplotlib 2.0 default style [#2320] Always index arrays with tuples in ImageAnimator [#2320] Added links to possible attrs for FIDO in guide [#2317] [#2289] Updated GitHub Readme [#2281] [#2283] Fix matplotlib / pandas 0.21 bug in examples [#2336] Fixes the off limb enhancement example [#2329] Changes to masking hot pixels and picking bright pixels examples [#2325] [#2319] Travis CI fix for numpy-dev build [#2340] Updated masking brightest pixel example [#2338] Changed TRAVIS cronjobs [#2338] Support array values for obstime for coordinates and transformations [#2342] [#2346] Updated Gallery off limb enhance example [#2337] Documentation fixes for VSO [#2354] [#2353] All tests within the documentation have been fixed [#2343] Change to using pytest-remotedata for our online tests [#2345] Fixed upstream astropy/numpy documentation issues [#2359] Documentation for Map improved [#2361] Fix the output units of pixel_to_world [#2362] Documentation for Database improved [#2355] Added test for mapsave [#2365] Documentation for Sun improved [#2369