[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")
```


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Should we consider adding postgresql as a travis-ci service? 

http://docs.travis-ci.com/user/using-postgresql/

Ideally we can still test the sqlite transfer even if we don't have postgres around.