Fix license in package.json

The project specifies a MIT license, but Apache 2.0 is written in package.json.

package.json

@@ -24,7 +24,7 @@
     "url": "git://github.com/Bttstrp/bootstrap-switch.git"
   },
   "bugs": "https://github.com/Bttstrp/bootstrap-switch/issues",
-  "license": "Apache-2.0",
+  "license": "MIT",
   "readmeFilename": "README.md",
   "devDependencies": {
     "babel-cli": "^6.22.2",