trim the trailing slash on https:// anchor links

If you pass true (4th param) to Html::anchor() it returns a trailing slash as it uses http_build_url() function instead of Uri::create(). 

Uri::create() returns a URI without a trailing slash. 

I've mimicked the behaviour of Uri::create() to remove the trailing slash.

Failed test results shown here https://gist.github.com/steadweb/5403721