Add in_testing config option to Nominatum

Checking against Rails.env.test? fails on Travis.

config/environments/test.rb

@@ -53,6 +53,8 @@ Growstuff::Application.configure do
 
 end
 
+Nominatim.in_testing = true
+
 Nominatim.add_stub(
   "Amundsen-Scott Base, Antarctica", {
     :latitude =>         -90.0,

lib/nominatim.rb

@@ -4,8 +4,13 @@ require 'json'
 
 class Nominatim
 
+  # class-level instance variable, see
+  # http://www.railstips.org/blog/archives/2006/11/18/class-and-instance-variables-in-ruby/
+  class << self; attr_accessor :in_testing end
+  @in_testing = false
+
   def self.geocode(place)
-    if Rails.env.test?
+    if self.in_testing
       return stubs[place]
     end
     json = open(