Add jasmine.useRealClock

This is the only way to unmock the _.now function uses
by _.debounce and _.throttle, since package specs don't
necessarily have access to core's copy of underscore-plus

Signed-off-by: Nathan Sobo <nathan@github.com>

spec/spec-helper.coffee

@@ -213,6 +213,11 @@ jasmine.snapshotDeprecations = ->
 jasmine.restoreDeprecationsSnapshot = ->
   Grim.deprecations = deprecationsSnapshot
 
+jasmine.useRealClock = ->
+  jasmine.unspy(window, 'setTimeout')
+  jasmine.unspy(window, 'clearTimeout')
+  jasmine.unspy(_._, 'now')
+
 addCustomMatchers = (spec) ->
   spec.addMatchers
     toBeInstanceOf: (expected) ->