Narrativeqa (with full text)
Following the uploading of the full text data in #309, I've added the full text to the narrativeqa dataset.

Few notes:
- Had some encoding issues using the default `open` so am using `open(encoding="latin-1"...` which seems to fix it. Looks fine.
-  Can't get the dummy data to work. Currently putting stuff at: 
    ```
    dummy
    |---- 0.0.0
            |- dummy_data.zip
                |-master.zip
                |   |- narrativeqa-master
                |       |- documents.csv
                |       |- qaps.csv
                |       |- third_party ......
                | 
                | - narrativeqa_full_text.zip
                |       | - 001.content
                |       | - ....
    ```
    Not sure what I'm messing up here (probably something obvious).