Add support for `schemes` in the specification

This enables Lagun to understand when to use https. If `schemes` is not
present in the specification the protocol of the serving host will be
used.

Fix for using serving host:port if not specified

Make request response box scrollable vertically

Add support for host and basePath in spec

This means that the request urls are no longer hardcoded to
http://petstore.swagger.io/v2/