Mark postponed issues with a label to make them easier to ignore?

[JukkaL]

Currently the decisions on some of the open issues seem to have been postponed until after Python 3.5. Maybe we should create an issue label for postponed issues to make it easier to see which issues are still unresolved.

Potential postponed issues:

• @overload outside stubs #72
• Type for heterogeneous dictionaries with string keys #28
• Interoperability of java.Util.Arraylist with typing.List (in Jython) #7

[gvanrossum]

Good idea. Done.