Updates readme to mention render-handlers by object-key.
Adds Render mediator and, RendererInterface and AbstractRenderer.
Updates composer.json to require smarty.
Updates composer.json to point to lmvc-utils' dev-master.
Adds MustacheHandler and updates AbstractHandler.
Adds merge option to setRenderArgs in AbstractHandler.
Adds JsonHandler.
Updates renderers' render() to take  param.