Make header comparison case-insensitive.
Make header comparison case-insensitive.

According to RFC 2616 Section 4.2 header field names are
case-insensitive. The code was looking for an exact match for the
header name, which made it fail when connecting to servers who
(correctly) used different casing for the Sec-WebSocket-Accept
headers.

Reported by Adam Denenberg.

Fixes #1.

wulczer/tsung_ws