pylint, comments, bug in parsing of HTTP headers

Hello,

thank you for vsltrans. We like it a lot and we're using it. Here are some changes I've made. The most notable change is in parsing of HTTP headers. There is a wrong assumption about contents of HTTP headers which do, at least in our case, contain another ':' which is used as a delimiter. As a result, you'll receive only partial data.
The rest of the commits are mostly polishing stuff. I hope, though, it will make code more friendly and easier to read.

Best regards,
Z.