Update grunt-connect-proxy version to "2.0"

It creates following error, if we do not update the version

```
Loading "connect_proxy.js" tasks...ERROR
>> TypeError: The super constructor to `inherits` must not be null or undefined.
Loading "Gruntfile.js" tasks...ERROR
>> TypeError: The super constructor to `inherits` must not be null or undefined.
Warning: Task "serve" not found. Use --force to continue.

Aborted due to warnings.
```
