Recursive -> Iterative

[samuelsonric]

I have made some functions iterative which were previously recursive. This avoids StackOverflowError errors.

[samuelsonric]

An even better approach for the function _timespacereadwrite_complexity would perhaps be to use this:

https://www.nowozin.net/sebastian/blog/streaming-log-sum-exp-computation.html

[GiggleLiu]

It looks good. Recurse makes our lives so much easier, I hope Julia can automatically expand the recursive function call to for loops in the future.