added support for scheme-less or protocol-agnostic 

- https?:|ftp: in valdation regex is now optional (therefore urls beginning with // validate)
- concatUri function gets another condition supporting uriString beginning with // by prepending the appropriate scheme
- added new helper function getProtocol that determines the protocol used to receive current site and returning scheme as string
Merge pull request #35 from cflack/master

added support for scheme-less or protocol-agnostic