Write initial docs
minor corrections (typos)
Added API section
Enabled Sphinx nitpicky mode
Added Sphinx extensions
Merge pull request #2 from keflavich/initial-docs

minor corrections (typos)
Fixed API links
Separate out sections into different pages
Use latest astropy objects.inv to fix API links
Improvements to docs
Fix typos
Merge pull request #15 from astrofrog/initial-docs

Write documentation