Mitigate getmoto#1793 by restricting maximum version for botocore.

botocore v1.11.0 changed it's internal implementation so that it now
uses a different library for HTTP requests. This means that moto's
mocking will not work, and test code will inadvertently call the live
AWS service.

As an interim solution to reduce the impact of this breakage, we
restrict the "required" (ie. recommended) version of botocore so that
users will be less likely to use an incompatible version, and will
receive a pip warning when they do.

setup.py

@@ -9,7 +9,7 @@
     "Jinja2>=2.7.3",
     "boto>=2.36.0",
     "boto3>=1.6.16",
-    "botocore>=1.9.16",
+    "botocore>=1.9.16,<1.11",
     "cookies",
     "cryptography>=2.0.0",
     "requests>=2.5",