port to py3
Improved stride handling
Include ArrayRef.h since it's used
Merge pull request #33 from nbecker/master

There's some kind of weirdness going on here in the tests - I keep getting a directory created that blocks a test executable from being created.  But I'm pretty sure it's not in anything you've done, despite the fact that I can only reproduce the bug on your branch.  I think I see where it is, but I'm out of time to fix it today.  So I'm going to merge your changes now, and fix the test problem tomorrow on another issue.