removing the need for the six module while keeping Py2/3 compatibility

[larkost]

I noticed that there is relatively little use of the six module in the project, and these minor changes remove the need altogether.

[sigmavirus24]

The io module works on Python 2.6+ and 3.0+ and has BytesIO on both. Why not just use that instead of incorrectly using StringIO?

[larkost]

From the presence of the six import I read implied pre-2.6 compatibility. If that is not needed then I can change this to be just from io import BytesIO. But as it is it has this effect on 2.6+.

[sigmavirus24]

I see absolutely no reason to support 2.5 unless @johnsheehan has a different opinion

[johnsheehan]

I don't think we need to support pre 2.6.

[kevin1024]

2.6 and up is fine with me.

[johnsheehan]

i'm not as well versed on six related issues as others so i'll leave this up to @sigmavirus24 to handle

[sigmavirus24]

You should remove the dependency from setup.py too then.

[larkost]

Done