[Reason] Adjust default print width.
[Reason] Adjust default print width.

Summary:
While discussing the formatting of Async bind function, it came to our
attention that the default print width is much too narrow. Changing it
to be `90`.

https://github.com/facebook/Reason/issues/113

Test Plan:

Reviewers:@samoht, @yunxing

CC:

chenglou/reason,ak3n/reason,facebook/reason,facebook/reason,facebook/reason,cristianoc/reason,let-def/reason,ak3n/reason,cristianoc/reason,yunxing/reason,chenglou/reason,yunxing/reason,yunxing/reason,yunxing/reason,chenglou/reason,let-def/reason,cristianoc/reason,let-def/reason,ak3n/reason,ak3n/reason