add a docs page
Merge pull request #29 from cdeil/first_docs_page

Docs?
Add interpolation routines
Tidied up files
Moved spherical overlap files to subdirectory
Implemented celestial interpolation from n-d slices
Merge pull request #32 from astrofrog/tidy-up

Moved spherical overlap files to subdirectory
Check that input and output WCS are equivalent (same number and order of axes)
Added ``Returns`` sections to docstrings
Added headers and __future__ imports
Fixed newline
Implemented suggestions by @keflavich
Remove unused variable
Merge pull request #31 from astrofrog/add-interpolation

Add interpolation routines
Move file
Import end-user functionality into top-level namespace
No 2to3
Add test files for interpolation
Add example from @astrofrog to Sphinx docs
Minor fixes pointed out by 2to3