BUG: error in handling a sqlalchemy type with arguments (instantiated type, not class)
I'm trying to use DataFrame().to_sql to input a time aware dataframe series. Here is an example of my code.

```
times = ['201412120154', '201412110254']

df = pd.DataFrame()
df['time'] = pd.to_datetime(times, utc=True)

df.time.to_sql('test', engine, dtype={'time': sqlalchemy.TIMESTAMP(timezone=True)})
```

The error I recieve is:

```
TypeError: issubclass() arg 1 must be a class
```

The following code works but obviously results in a postgresql column that is not timezone aware.

```
times = ['201412120154', '201412110254']

df = pd.DataFrame()
df['time'] = pd.to_datetime(times, utc=True)

df.time.to_sql('test', engine, dtype={'time': sqlalchemy.TIMESTAMP})
```

I'm using python 2.7, pandas 0.15.2, postsgresql 9.3 and SQLAlchemy 0.9.7. This same issue also occurs with sqlalchemy.DATETIME(timezone=True) vs sqlalchemy.DATETIME

Full Traceback:

```
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-161-ec79a553e6d0> in <module>()
----> 1 df.time.to_sql('test', w.engine, dtype={'time': sqlalchemy.TIMESTAMP(timezone=True)})

/home/stew/.pyenv/versions/p276/lib/python2.7/site-packages/pandas/core/generic.pyc in to_sql(self, name, con, flavor, schema, if_exists, index, index_label, chunksize, dtype)
    964             self, name, con, flavor=flavor, schema=schema, if_exists=if_exists,   
    965             index=index, index_label=index_label, chunksize=chunksize,
--> 966             dtype=dtype)
    967 
    968     def to_pickle(self, path):

/home/stew/.pyenv/versions/p276/lib/python2.7/site-packages/pandas/io/sql.pyc in to_sql(frame, name, con, flavor, schema, if_exists, index, index_label, chunksize, dtype)
    536     pandas_sql.to_sql(frame, name, if_exists=if_exists, index=index,
    537                       index_label=index_label, schema=schema,
--> 538                       chunksize=chunksize, dtype=dtype)
    539 
    540 

/home/stew/.pyenv/versions/p276/lib/python2.7/site-packages/pandas/io/sql.pyc in to_sql(self, frame, name, if_exists, index, index_label, schema, chunksize, dtype)
   1162             import sqlalchemy.sql.type_api as type_api
   1163             for col, my_type in dtype.items():
-> 1164                 if not issubclass(my_type, type_api.TypeEngine):
   1165                     raise ValueError('The type of %s is not a SQLAlchemy '
   1166                                      'type ' % col)

TypeError: issubclass() arg 1 must be a class
```
