Expand SDSS query

Expanded the SDSS by adding photoobj_fields and specobj_fields to
query_region_async and _args_to_payload parameters so that the user can
retrieve any field from the PhotoObjAll object (see
http://cas.sdss.org/dr4/en/help/browser/description.asp?n=PhotoObjAll&t=
U)
Display error to user

Fixed bug where an error message from the server caused the code to
throw a ValueError exception without displaying the error message from
the server
Updated print function for py3
Changed exception to RemoteServiceError
Removed encode('ascii') for py3 compatibility
Forgot one of the encode('ascii') lines
Attempting to fix py3 encoding error
Merge pull request #375 from fred3m/master

Expand SDSS query