MNT: Mark incompatible with numpy 1.19, Sphinx 3

Author: effigies

setup.cfg

@@ -31,7 +31,7 @@ provides =
 [options]
 python_requires = >=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,<3.9dev
 install_requires =
-    numpy >=1.8
+    numpy >=1.8,<1.19dev
     six >=1.3
     bz2file ; python_version < "3.0"
 tests_require =
@@ -45,7 +45,7 @@ include_package_data = True
 dicom =
     dicom >=0.9.9
 doc =
-    sphinx >=0.3
+    sphinx >=0.3,<3
 test =
     nose >=0.11
 all =