Adjust tests for Travis CI build.

Adjusted `t/sdk/proxy.t.js` for Linux. On Darwin the server process
exits successful, while on Linux the exit is null and the signal is
reported.

Updated the `stdout` listener to fire only once. It was firing twice on
Travis CI, causing the test to setup a second proxy which failed because
the ports were already bound.
Merge branch `proxy-test` into `travis-ci`.

Conflicts:
	t/sdk/proxy.t.js