Allow most iterables as return values.

[untitaker]

Allows you to directly yield data from the view instead of having to make an inner function whose return value you pass to flask.Response.

[mitsuhiko]

-1 on this. There are too many options you need to consider when dealing with streaming and there is the other disadvantage that nothing in the function fires until you iterate once. This leads to hard to debug bugs. The extra level of indirection solves this nicely.