phantomjs: Handle cases of PhantomJS crash during remote check-in/out

Closes chfoo/wpull#194
Add phantomjs.PhantomJSClient.close().
requirements: Require trollius>=1.0.2
proxy: Support add and extract cookies for PhantomJS.

Closes chfoo/wpull#95
phantomjs_test: Handle case where mock crash has no reply.