Refactor I/O
Fix failing tests
Added read class method, and placeholder read/write for StokesSpectralCube
Update docs
Added missing file from previous commits
Fix remaining references to read
Fix test failures
Allow kwargs to be passed to fits.open
Added more extensions for FITS
Read BUNIT into metadata
Merge pull request #83 from astrofrog/refactor-io

Refactor I/O
Create MomentMap class to encompass the moment map with WCS information, and make it easy to get an HDU object using the ``hdu`` attribute.
Added documentation about MomentMap
Use Projection instead of MomentMap
Add a test that the copy= argument works for Projection
Merge pull request #54 from astrofrog/moment-map-class

Return moments as HDU objects or CubeSlice objects
Added installation docs, fixed read -> SpectralCube.read in quick start
Added link to yt example
Implemented @keflavich's comments
Merge pull request #85 from astrofrog/install-docs

Added installation docs