fix net-http-persistent timeout detection on Ruby 2.0

Re-enable timeout test because drbrain/net-http-persistent#33 got fixed
in net-http-persistent 2.8
fix Typhoeus proxy support
prevent Typhoeus from using "Expect: 100-continue" on PUT

It seems whether the request method for Typhoeus request is `:put` or
"PUT" decides whether it will use "Expect: 100-continue" when performing
that request. In our test suite, such PUTs would fail randomly against
WEBrick which doesn't have stable support for 100 Continue. This seems
to be a problem with WEBrick, not Typhoeus.

This also speeds up these requests, which WEBrick was slow to process
even if they've succeeded.

"Expect: 100-continue" is a mode where the client sends this header, but
doesn't send the body of the request until the server inspects the
headers and decides it wants to allow the request by sending
"HTTP/1.1 100 Continue" back.
rewrite test script in bash

The HTTP server is now started in a subprocess, not a thread. Running it
in a Ruby thread had all sorts of problems on different Rubies, such as
random failures on Rubinius.

The new script also avoids starting the HTTP server if not needed, e.g.
if filtering arguments have been used to select only the non-adapter tests.

The script dumps the server log to stdout if any tests failed on Travis.

Avoids auto-starting the debugger because it blocks for input in Rubinius
https://travis-ci.org/lostisland/faraday/jobs/5956815