Added _args_to_payload function
Modified get_spectra_async to accept coordinates
Modified get_images to accept coordinates
Fixed handling of multiple bands
Fixed SQL query to avoid duplicate images or spectra
Updated tests for new API and add new tests
Removed unused imports
PEP8 cleanup
Updated documentation
Merge pull request #260 from loicseguin/sdss-api

Improve SDSS API compliance
Add query_specobj and query_photoobj
Add tests for query_specobj and query_photoobj
Make FileContainer accept the same args as get_readable_fileobj
Merge pull request #261 from loicseguin/filecontainer-timeout

Make FileContainer accept the same args as get_readable_fileobj
Add timeout for query_region
Make FileContainer accept the same args as get_readable_fileobj
Add optional timeout argument to SDSS methods
Merge branch 'master' into sdss-timeout
Use send_request for proper handling of timeout errors
Handle timeout exceptions in FileContainer