Add a options to config the index file path

[itrethan]

Current implement default to serve /index.html.

But in express it has express.static(app.get('appPath'), {index: 'landing/index.html'})

This achieve the same thing.

[itrethan]

anybody have a look at this?

[SpaceK33z]

@itrethan, if you fix the merge conflict I'll merge it.

[SpaceK33z]

@itrethan, still interested in finishing this?

[itrethan]

@SpaceK33z I opened another one, please look at here #123