Patch to close #529.

Subclassed the download method in GOES lightcurve to specify a custom filename
from the uri which is then passed to LigtCurves download.

Added the ability to specifiy custom filename to LightCurve._download
add tests
Improved tests (think only works on 2.7) removed print.
fix test on 2.6
Merge pull request #559 from Cadair/0.3_#529

Patch to close #529.