Changed printpf back to original format and modified files calling the class, to open the files simply to append (as opposed to writing binary). Changed format of the files so that the program only writes to stdout iff a file is not specified. All changes made should be compatible with both python 2 and python 3.
Merge pull request #15 from charlie0389/py3printpf

Improvements to printpf, runpf, runopf and runuopf in regards to output