Fix parsing for URIs with a : in the authority (dart-lang/stack_trace#69)

Add a `$` to enforce that the `:(\d+)` is at the end of the String. The
previous regex could pick up too little - we end up with
`http://localhost` as the URI and the port as the line.

Switch from `pub.dartlang.org` to `example.com` to avoid references
to legacy URLs.