Add API to get binary parse as seen in the SNLI corpus

Looking for following input and output pair:

**Input**

```
"sentence1": "This church choir sings to the masses as they sing joyous songs from the book at a church."
```

**Output**

```
"sentence1_binary_parse": "( ( This ( church choir ) ) ( ( ( sings ( to ( the masses ) ) ) ( as ( they ( ( sing ( joyous songs ) ) ( from ( ( the book ) ( at ( a church ) ) ) ) ) ) ) ) . ) )",
```