Revamped coordinates getting started for APE5 scheme
Update separations for APE5
Fix typo in test_api -> test_api_ape5
initial reorganization of coordinates docs for APE5
tweaks to angles.rst
reorganized match/sep stuff
add todo noe in formatting.rst
more APE5 reorganization
overview for APE5 and associated changes
further APE5 doc updates
sphinx warning fixes
Documentation for representation classes
Implemented comments by @eteq
Merge pull request #31 from astrofrog/coordinates-docs-representations

Documentation for representation classes
Merge pull request #2513 from eteq/coordinates-docs-update-ape5

Update coordinates docs for APE5