Template engine

[rogelio-o]

Add template engine to be used in the response method render. The way to render a view have to be abstracted in order to apply any template engine, only implementing an interface and configuring it in the app configuration.

The process to render a template will be:

1. Get the file from the S3 bucket configured as views container.
2. Use the configured render interface to render the previous obtained file with the given parameters.
3. Send the response with the HTML code of the rendered view or call the callback function with the code if it exists.

As default render engine, Pug will be used.

[rogelio-o]

In order to maintain the framework lightweight, no default render engine is set. The user can add the template engine in a function that implements the interface ITemplateRenderer.