Pretend we work with flask 0.6.
Pretend we work with flask 0.6.

We don't use very much of flask-restful, and history has shown the
part we do use *is* compatible with flask 0.6.  Since our website uses
0.6.1, I want to make this dep consistent with that so can start using
pip to install flask-restful rather than doing it manually.

Auditors: benkraft

Test plan:
Fingers crossed

Khan/flask-restful