Add links to typeshed and typing trackers.

Author: gvanrossum

README.md

@@ -8,7 +8,14 @@ Got a question? File an issue!
 ------------------------------
 
 We don't have a mailing list; but we are always happy to answer questions
-filed as issues in our [tracker](https://github.com/python/mypy/issues).
+filed as issues in our trackers:
+- [mypy tracker](https://github.com/python/mypy/issues)
+  for mypy isues
+- [typeshed tracker](https://github.com/python/typeshed/issues)
+  for issues with specific modules
+- [typing tracker](https://github.com/python/typing/issues)
+  for discussion of new type system features (PEP 484 changes) and
+  runtime bugs in the typing module
 
 
 What is mypy?