Changed TC SVG from wikimedia to work
Changed example to typical "six-pack" configuration

Changed the example to show a typical “six-pack” instrument
configuration with the addition of the turn-coordinator instrument.
Adds attribution for SVG source

adds source for TC SVG source (wikimedia) and notes that the angle of
the “airplane” in the turn coordinator would show the opposite angle of
the attitude indicator, as the AI mirrors what you see out the window,
and the TC airplane mirrors what the wings are doing.
Merge pull request #4 from canuk/add-turn-coordinator

Adds turn coordinator and re-configures example for standard "six-pack"