Transform

closes #67 and closes #66.  Adds transformations of the CCDData object although uncertainties may not be handled correctly.  It also handles rebinning of ccddata objects. 
This tests round-tripping from (10,10) → (20, 20) → (10, 10); should there be a similar test for (10, 10) → (5, 5) → (10, 10)? Though in that case you don't expect to get back the same result.