Fix hypothesis dependency (#213)

Summary:
Pull Request resolved: #213

caffe2 uses min_satisfying_examples, which was removed in v4.0 of
hypothesis. This diff makes sure we depend on an earlier version until this
is fixed upstream

Reviewed By: m3rlin45, chenyangyu1988

Differential Revision: D13704590

fbshipit-source-id: 057a33ecd3978b8c11077f475eac3c150d87f7dd

requirements.txt

@@ -1,6 +1,6 @@
 click
 future
-hypothesis
+hypothesis<4.0
 joblib
 numpy
 onnx