Introduce runMulti that can take filenames and code strings mixed together.

On the server side, it can be convenient to provide the JS code to run as string
instead of file to read on the disk.
It is also very convenient to be able to mix the two types.
The source code is on index 0
Use the new method name.
Merge pull request #3 from ant0ine/master

Introduce runMulti that can take filenames and code strings mixed togeth...