Implement command line passing to work to emrun when --emrun is passed.

This commit adds support to emrun to pass

'emrun filename.html arg1 arg2 arg3'

which will spawn the URL

'http://localhost:6931/filename.html?arg1&arg2&arg3'

which will get routed to Module['arguments'], so that the application main() will then receive the arguments in argc and argv when built with --emrun.