Bug in server/scriptDownloader.js

This appears to have been introduced in the commit (b7a4abd2e7ddffeabbeb43c5aaa9428aad40dec0) converting this script from coffeescript to js.

fs.readFileSync() returns a buffer if no encoding is provided. Either pass an encoding or, as this fix does, call toString(). An error was being created when .replace() was being called on the buffer object at line 56