[WIP] Feature/csv to sql natively

When finished, this PR should address #352. New `into` function calls out to to native COPY function of various DBs.  Has optional `if_exists` argument (similar to pandas) to handle three cases: replace, append, and fail

```python
into(sql,csv, if_exists="replace")
```

This PR currently handles the native copy calls for:

- PostgreSQL
- MySQL
- SQLITE


- [x] Travis CI PostgreSQL Testing
- [ ] Travis CI MySQL Testing

<!---
@huboard:{"order":342.75,"milestone_order":454,"custom_state":""}
-->

datetimes will also work.  I used date because they are simply dates:
https://github.com/quasiben/blaze/blob/feature/csv_to_sql_natively/blaze/tests/dummydata.csv#L2