chore(package): update gulp-footer to version 2.0.1

Closes #26

Author: greenkeeper[bot]

package.json

@@ -12,7 +12,7 @@
   "devDependencies": {
     "better-assert": "1.0.2",
     "gulp": "3.9.1",
-    "gulp-footer": "1.0.5",
+    "gulp-footer": "2.0.1",
     "gulp-header": "1.8.8",
     "gulp-mocha": "3.0.1",
     "gulp-rename": "1.2.2",