Support hyperlinks (iTermin2, Gnome Terminal)

[Jeff Quast]

At time of this writing, iTerm2 and Gnome Terminal support the ability to place hyperlinks in text, https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda

printf '\e]8;;http://example.com\e\\This is a link\e]8;;\e\\\n'

Our implementation would probably appear as,

Terminal().hyperlink('http://www.example.com', 'This is a link')

As named parameters url and text.

[Jeff Quast]

In PR #147