sqlalchemy/dialects/postgresql/pgjson:
 - Fixed reference to HSTORE
 - Corrected spelling of SQLAlchemy

 sqlalchemy/dialects/postgresql/psycopg2:
 - Added psycopg2 specific wrapper type for JSON which uses inherent json deserialization facilities
 - Added code to detect and utilize the JSON wrapper if psycopg2 >= 2.5

test/dialect/postgresql/test_types:
- removed reference to use_native_hstore