Cleaned up linting errors

Author: jacobawenger

.jshintrc

@@ -1,5 +1,6 @@
 {
   "predef": [
+    "define",
     "module",
     "Firebase"
   ],
@@ -15,4 +16,4 @@
   "trailing": true,
   "undef": true,
   "unused": true
-}
+}

build/header

@@ -9,6 +9,7 @@
  */
 
 ;(function (root, factory) {
+  "use strict";
   if (typeof exports === "object") {
     // CommonJS
     module.exports = factory();
@@ -18,8 +19,8 @@
       return (root.ReactFireMixin = factory());
     });
   } else {
-    // Global Variables
+    // Global variables
     root.ReactFireMixin = factory();
   }
 }(this, function() {
-  "use strict";
+  "use strict";