install.json: JSON strings must be enclosed in double quotes

The JSON spec only accepts double-quoted strings.   Planex
now uses Python's JSON library, which enforces this requirement,
whereas the old demjson library did not.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #44 from euanh/master

install.json: JSON strings must be enclosed in double quotes