Drop IE11 and Safari 9

per discussion in sinonjs#375 and sinonjs/sinon#2359

Author: fatso83

.min-wd

@@ -2,12 +2,5 @@
   "sauceLabs": true,
   "browsers": [{
     "name": "firefox"
-  }, {
-    "name": "internet explorer",
-    "version": "11"
-  }, {
-    "name": "safari",
-    "platform": "OS X 10.11",
-    "version": "9.0"
   }]
 }