Update Rack apps for 1.9.2

[maxhawkins]

I ran into some trouble while trying to use sproutcore with pow.cx. I added this config.ru to my sproutcore project

require 'rubygems'  
require 'bundler/setup'

require 'sproutcore'  

root = Pathname(__FILE__).dirname.expand_path  
project = SC::Project.load_nearest_project(root, :parent => SC.builtin_project)  
service = SC::Rack::Service.new(project)  
run service

But ran into errors while trying to fetch "/sc/targets.json"

It turns out the rack app that serves that file was passing a raw string as content and strings don't respond to #each as of 1.9.2 so it choked. This change makes SC::Rack::Dev and all of the other Rack apps in abbot that return a string return an array instead.

Sorry there aren't any failing tests. I couldn't find a convenient place to add them. All of the tests still pass.