read_sql/to_sql should accept database URI as con parameter
Hello,

it will be nice if `read_sql` (and so `read_sql_query` and `read_sql_table` could directly accept database URI as `con` parameter
http://pandas.pydata.org/pandas-docs/stable/generated/pandas.read_sql.html

So we could do

```
import pandas as pd
uri = 'dialect+driver://username:password@host:port/database'
query = 'SELECT * FROM table'
df = pd.read_sql(query, uri)
```

instead of :

```
import pandas as pd
from sqlalchemy import create_engine
uri = 'dialect+driver://username:password@host:port/database'
engine = create_engine(uri)
query = 'SELECT * FROM table'
df = pd.read_sql(query, engine)
```

Kind regards

PS: this kind of idea is also used by Blaze / odo
http://blaze.pydata.org/
http://odo.readthedocs.org/

PS2: A similar approach could maybe also apply to `to_sql(...)`
