Fixed syntax error in bower.json

`bower.json` has syntax error and bower can't install qrcode.js.

```sh
$ bower install qrcode.js=https://github.com/davidshimjs/qrcodejs.git
bower qrcode.js#*           not-cached https://github.com/davidshimjs/qrcodejs.git#*
bower qrcode.js#*              resolve https://github.com/davidshimjs/qrcodejs.git#*
bower qrcode.js#*             checkout master
bower qrcode.js#*           EMALFORMED Failed to read /var/folders/s2/j1hmfp3s2814bqll10pjny180000gn/T/hanai/bower/qrcode.js-6803-fUODrr/bower.json

Additional error details:
Unexpected token ]
```