Fix #118: Cannot find module '${HOME}/host.js'

[justfortherec]

It appears that Firefox starts the native client from $HOME as the working directory. That leads to the script resolving the relative path host.js as $HOME/host.js.

This fix prefixes the host.js filename with the directory of the run.sh file. Now it works regardless of the working directory and regardless of the directory in which run.sh and the JavaScript files are located (as long as they are in the same location).

Fix: andy-portmen/native-client#118