Handle a couple edge-cases

If jQuery isn't loaded until after jasmine-fixture:
* allow subsequent calls to affix() to correct for this
by initializing jasmineFixture if jQuery is available
at call-time
* If jQuery is still unavailable, then throw an error
when the user attempts to affix()

Fixes #27

app/js/jasmine-fixture.coffee

@@ -43,7 +43,13 @@
   if $
     jasmineFixture = root.jasmineFixture($)
   else
-    throw new Error("jasmine-fixture requires jQuery to be defined at window.jQuery or window.$")
+    root.affix = ->
+      nowJQueryExists = window.jQuery || window.$
+      if nowJQueryExists?
+        jasmineFixture = root.jasmineFixture(nowJQueryExists)
+        affix.call(this, arguments...)
+      else
+        throw new Error("jasmine-fixture requires jQuery to be defined at window.jQuery or window.$")
 
 )(window.jQuery || window.$)