Added .travis.yml for testing
Ensure test data is created and other fixes
Merge pull request #19 from astrofrog/travis

Added .travis.yml
Use np.isfinite as a mask function
Refactored masks to enable non-array masks, and implemented function masks
Fix bugs in masking
Added tests for masking
Added tests for functional mask
Fix slab for functional masks
Compare WCS using to_header()