Databases Docs: Small Typo (move-coop#443)

* Update databases.rst

docs/databases.rst

@@ -75,24 +75,24 @@ Quick Start
    from parsons import Postgres
 
    # Instantiate Postgres from environmental variables
-   mysql = Postgres()
+   pg = Postgres()
 
    # Instantiate Postgres from passed variables
-   Postgres = Postgres(username='me', password='secret', host='mydb.com', db='dev', port=3306)
+   pg = Postgres(username='me', password='secret', host='mydb.com', db='dev', port=3306)
 
    # Instantiate Postgres from a ~/.pgpass file
-   Postgres = Postgres()
+   pg = Postgres()
 
 **Quick Start**
 
 .. code-block:: python
 
    # Query database
-   tbl = postgres.query('select * from my_schema.secret_sauce')
+   tbl = pg.query('select * from my_schema.secret_sauce')
 
    # Copy data to database
    tbl = Table.from_csv('my_file.csv') # Load from a CSV or other source.
-   postgres.copy(tbl, 'my_schema.winning_formula')
+   pg.copy(tbl, 'my_schema.winning_formula')
 
 .. autoclass:: parsons.Postgres
    :inherited-members: