[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")
```

- [ ] Travis CI PostgreSQL Testing
- [ ] Travis CI MySQL Testing

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@quasiben 
    /Users/kdodia/miniconda/envs/py2/lib/python2.7/site-packages/blaze/data/sql.pyc in into(sql, csv, if_exists, **kwargs)
        336     header = retrieve_kwarg('header') or csv.header
        337     lineterminator = retrieve_kwarg('lineterminator') or u'\n'
    --> 338     skiprows = retrieve_kwarg('skiprows') or int(csv.header) #hack to skip 0 or 1
        339 
        340     copy_info = {'abspath': abspath,
    
    TypeError: int() argument must be a string or a number, not 'NoneType'