Update shapely dependency to version 1.6.4 for Python 3.7 compatibility

Author: jonmmease

tox.ini

@@ -63,7 +63,7 @@ deps=
     optional: jupyter==1.0.0
     optional: pandas==0.19.2
     optional: scipy==0.18.1
-    optional: shapely==1.6.3
+    optional: shapely==1.6.4
     optional: geopandas==0.3.0
     optional: pyshp==1.2.10