Failing test for #364
Fix #364

This cleans up our use of bytestrings in make_franken_headers to avoid
implicit casts to unicode.
Here's a failing test for headers.raw w/ non-ASCII

Surfaced in #364.
Here's a fix for headers.raw w/ non-ASCII
Clean up implicit casts in test_http{basic,digest}
Note a second StackOverflow link in comment
Merge pull request #365 from gittip/issue364

root out implicit casts from header parsing