Fix version compatibility issue between browserify and grunt-browserify

Thix PR fix a compatibility  issue between grunt-browserify and browserify

grunt-browserify wants browserify@>=2.35 < 3.0.0

```
npm install

npm ERR! peerinvalid The package browserify does not satisfy its siblings' peerDependencies requirements!
npm ERR! peerinvalid Peer grunt-browserify@1.2.11 wants browserify@>=2.35 < 3.0.0
```