use numpy == 1.17.3

Author: jswhit

.travis.yml

@@ -4,8 +4,8 @@ env:
         - BUILD_COMMIT=v1.5.4rel
         - PLAT=x86_64
         - UNICODE_WIDTH=32
-        - NP_BUILD_DEP=1.13.3
-        - NP_TEST_DEP=1.13.3
+        - NP_BUILD_DEP=1.17.3
+        - NP_TEST_DEP=1.17.3
         - WHEELHOUSE_UPLOADER_USERNAME=travis-worker
         # Following generated with
         # travis encrypt -r MacPython/netcdf4-python-wheels WHEELHOUSE_UPLOADER_SECRET=<the api key>