Added emrun utility that allows running .html files in a browser like they were normal executables. For more information, see https://groups.google.com/forum/#!topic/emscripten-discuss/t2juu3q1H8E .
Added test to check that emrun stdout, stderr and process exit code capture work.
Add machinery that detects whether a html page was built with --emrun command line flag, and print a warning if not done so.
Implemented --emrun linker flag to emcc, which is a helper that makes the compilation output emrun-compatible.