Fix WriteHTMLForTracesToFile

Turn out my last fix doesn't actually work. Somehow able to get a window machine to test this fix. Also clean up compressed_file logic which I believe is unnecessary.
To test this change on Windows, run:
python run_tests trace2html
So the purpose of this is to compress the trace data? This seems like the wrong way to do it. Can we just use zlib.compress(str) instead?