Using PostgreSQL, Model.create() leaves connection idle in transaction
Duplicate of #353. The latest pypi release (2.2.4) has the fix.
 Confirmed, thanks.

peewee==2.1.7
psycopg2==2.5.1
psql (9.3.4)
Python 3.4.0 (default, Apr 28 2014, 13:52:15) 

The following code snippet will reproduce it:

``` python
from peewee import *
db = PostgresqlDatabase('dbname', user='user', password='password',
                        host='localhost')
db.connect()

class Test(Model):
    class Meta:
        database = db
    pk = PrimaryKeyField()
    val = IntegerField()
```

Test.create_table(fail_silently=True)
Test.create(val=1)

The postgresql log shows this:

2014-05-15 09:14:50 MDT LOG:  statement: COMMIT
2014-05-15 09:14:54 MDT LOG:  statement: BEGIN
2014-05-15 09:14:54 MDT LOG:  statement: INSERT INTO "test" ("val") VALUES (1)
2014-05-15 09:14:54 MDT LOG:  statement: COMMIT
2014-05-15 09:14:54 MDT LOG:  statement: BEGIN
2014-05-15 09:14:54 MDT LOG:  statement: SELECT CURRVAL('"test_pk_seq"')

The problem is there is no COMMIT following that last SELECT, leaving the transaction open. On PostgreSQL this can cause problems _even in other databases on the same server_. See http://www.postgresql.org/message-id/4C6CEE4202000025000348D6@gw.wicourts.gov

I'll submit a pull request with a patch to fix.
