ndg-httpsclient is not needed to run tests.

--- requests-toolbelt-1.0.0/tox.ini.orig
+++ requests-toolbelt-1.0.0/tox.ini
@@ -17,7 +17,6 @@
     pytest
     mock;python_version<"3.3"
     pyopenssl
-    ndg-httpsclient
     betamax>0.5.0
     trustme
 commands =