Fix a problem related to shell command calls from a spaced path

Hello guys,

I found a problem related to spaced paths.  When yapp.js is being called from a spaced path (like /Users/rodrigoayala/My Projects/tv.js), the execution of the compiler fails because /bin/sh doesn't know how to handle a command with unescaped spaces.

I've tested this fix locally with tv.js project, pointing to yapp.js located on my repo, and it works fine.