Fixed Control Characters in JSON

This should fix mods like Big Box of Loot http://community.playstarbound.com/index.php?resources/fireflys-big-box-of-loot-collaboration.883/

The modinfo file has an unescaped multiline string in it. Digging around and found the information below:

From: http://docs.python.org/3.3/library/json.html
If strict is False (True is the default), then control characters will
be allowed inside strings. Control characters in this context are those
with character codes in the 0-31 range, including '\t' (tab), '\n', '\r'
and '\0'.