Prevent double path separators in redirect URL.

+ The base URL path was set to '/providence', which was then part
  of an array joined using '/' separator, which resulted in a '//'
  in the URL, which was causing a problem with redirects on logging
  in, and preventing login under some circumstances.  This ensures
  that all components are trimmed of leading and trailing '/'
  characters before joining.
Merge pull request #163 from leftclickben/FixLoginRedirectIssueUpstream

Prevent double path separators in redirect URL.