Get progress information with DataFrame.apply()
I'm looking into the code to see if this change would be a major or minor undertaking. I don't know what your opinion is about it.

I have a large data frame and a complicated map function I want to apply to all rows. Calling apply along axis  1 has been running for an hour now, and I have no idea if this will take until an hour from now or until tomorrow or until next week. I think a some progress reporting would be instrumental in helping a user decide quickly if its reasonable to use pandas or if moving to another library / stack is worthwhile.