Resolve issue avoiding preview-task to run

First problem:

    $ grunt preview-live
    Running "jshint:gruntfile" (jshint) task

       Gruntfile.js
    >> ES5 option is now set per default

    >> 1 error in 1 file
    Warning: Task "jshint:gruntfile" failed. Use --force to continue.

    Aborted due to warnings.

As mentioned in [this article](http://jslinterrors.com/es5-option-is-now-set-per-default "ES5 option is now set per default")
and discoused in [this issue](https://github.com/jshint/jshint/issues/1137)
The solution is to remove the option `ES5` from `.jshintrc`.

Second problem:

    $ grunt preview-live
    Running "jshint:gruntfile" (jshint) task
    >> 1 file lint free.

    Running "jshint:app" (jshint) task
    >> 2 files lint free.

    Running "jshint:test" (jshint) task
    >> 1 file lint free.

    Running "qunit:files" (qunit) task
    Testing test/index.html .OK
    >> 1 assertions passed (95ms)

    Running "clean:files" (clean) task

    Running "requirejs:compile" (requirejs) task

    Running "concat:dist" (concat) task
    File dist/require.js created.

    Running "uglify:dist" (uglify) task
    File dist/require.min.js created: 330.82 kB → 101.33 kB

    Running "connect:production" (connect) task
    Warning: Arguments to path.resolve must be strings Use --force to continue.

    Aborted due to warnings.

Rewrited the `middleware` option following
[the documentation](https://www.npmjs.org/package/grunt-contrib-connect)

And:

    $ grunt preview-live
    Running "jshint:gruntfile" (jshint) task
    >> 1 file lint free.

    Running "jshint:app" (jshint) task
    >> 2 files lint free.

    Running "jshint:test" (jshint) task
    >> 1 file lint free.

    Running "qunit:files" (qunit) task
    Testing test/index.html .OK
    >> 1 assertions passed (64ms)

    Running "clean:files" (clean) task

    Running "requirejs:compile" (requirejs) task

    Running "concat:dist" (concat) task
    File dist/require.js created.

    Running "uglify:dist" (uglify) task
    File dist/require.min.js created: 330.82 kB → 101.33 kB

    Running "connect:production" (connect) task
    Waiting forever...
    Started connect web server on http://0.0.0.0:8000