FIX: Fix np.fromfile bug better

Let's just make sure Travis is happy. There is a bug with `np` that shows up on some systems, on some versions of Python, where `np.fromfile` incorrectly advances the file pointer. I saw this happen on Windows (Python2.7) last year, and never fixed it because I couldn't track down the issue. I've now been seeing it on Python3.3 under Linux. Changing `rb` to `rb+` worked, but this is less clean than just setting `buffering=0` and leaving mode as `rb` (which is what this PR does).