Remove kombu-sqlalchemy and use database string in modern kombu-proper format

Previously we were using kombu-sqlalchemy the library for sqlalchemy
support.  Newer kombu has support for this internally, so we're using
that.  Requires changing a celery setting and also removing
kombu-sqlalchemy from your path.

I hope the process of removing kombu-sqlalchemy from one's path
doesn't confuse too many people...!

mediagoblin/config_spec.ini

@@ -117,7 +117,7 @@ CELERY_RESULT_DBURI = string(default="sqlite:///%(here)s/celery.db")
 
 # default kombu stuff
 BROKER_TRANSPORT = string(default="sqlalchemy")
-BROKER_HOST = string(default="sqlite:///%(here)s/kombu.db")
+BROKER_HOST = string(default="sqlalchemy+sqlite:///%(here)s/kombu.db")
 
 # known booleans
 CELERY_RESULT_PERSISTENT = boolean()

setup.py

@@ -64,7 +64,6 @@ setup(
         'Markdown',
         'sqlalchemy',
         'sqlalchemy-migrate',
-        'kombu-sqlalchemy',
         ## For now we're expecting that users will install this from
         ## their package managers.
         # 'lxml',