Do not support Emacs 23.
Do not run tests in Emacs 24.1 and 24.2 on Travis.

The function with-timeout does not seem to work fully. Running tests
will output error:

(void-function prodigy-init-async-timeout)
Use magnars reporter.
Curl error messages seem do differ.

Maybe depending on what version. Travis had another message than what I
had locally.