introduced command.js
Added change background
Reduced execution delay by a bit
Set to reset to default sprite/background if user left the textbox blank
Fixed 404 on case-sensitive file systems.
Copy files in the img folder to the build path.
Added different scaling modes for background image.
Merge pull request #6 from xcchan/master

Added change background command to interpreter
Merge remote-tracking branch 'origin/master' into cmd
Merge remote-tracking branch 'visualIDE_yj/master' into cmd
Merge branch 'master' into cmd

Conflicts:
	js/command.js