Throw a recognizable Error message when fail outside of a spec.

Fixes #1017

src/core/Env.js

@@ -532,6 +532,10 @@ getJasmineRequireObj().Env = function(j$) {
     };
 
     this.fail = function(error) {
+      if (!currentRunnable()) {
+        throw new Error('\'fail\' was used when there was no current spec, this could be because an asynchronous test timed out');
+      }
+
       var message = 'Failed';
       if (error) {
         message += ': ';