Dict View Issue in IO data.py
If using python 3.4 there will always be a TypeError thrown in the data.py 
lines 330-332

```
    if len(stocks) > 0 and len(failed) > 0:
        df_na = stocks.values()[0].copy()
        df_na[:] = np.nan
```

For python 3 users the stock.values needs to be wrapped because it's returning a view not a list

```
        df_na = list(stocks.values())[0].copy()
```
