Properly handle languages created not as extensions, post 9.2.  Fixes #103.

  Third time is a charm.

 * pyrseas/dbobject/language.py (LanguageDict.query): Do not include
   languages wrapped by extensions in query.
 * tests/dbobject/test_{extension, language}.py: New or modified
   tests, courtesy of DVarrazzo.
 * tests/dbobject/test_function.py: Moved bug 103 test to
   test_language.py.
Merge branch 'r0.7'
Properly handle an external language like plv8. Fixes #97.

  * pyrseas/database.py (Database._link_refs): Change query against
    pg_pltemplate to join of pg_language and pg_depend.
    (Database.diff_map): Move extensions._drop further down.
  * pyrseas/dbobject/extension.py (ExtensionDict.diff_map): Mark
    extensions for dropping.
Fix tests committed in 8c9f59e.
Merge branch 'r0.7'