Merge pull request #14520 from velconia/change_requirements

Change requirements to support python 3.7

python/requirements.txt

 requests==2.9.2
-numpy>=1.12,<=1.14 #TODO:change to ">=1.12" when numpy fix bug in 1.15 and higher version
+numpy>=1.12
 protobuf==3.1
 recordio>=0.1.0
 matplotlib==2.2.3 # TODO: let python3 paddlepaddle package use latest matplotlib