Ensure popen is required from closure/compiler

Author: josh

lib/closure-compiler.rb

@@ -13,5 +13,4 @@ module Closure
 end
 
 require 'stringio'
-require 'closure/popen'
 require 'closure/compiler'

lib/closure/compiler.rb

@@ -1,3 +1,5 @@
+require 'closure/popen'
+
 module Closure
 
   # We raise a Closure::Error when compilation fails for any reason.
@@ -57,4 +59,4 @@ def command
     end
 
   end
-end
+end