Wrong origin in CoreGraphicsIntro's coordinate.png

[akerenyi]

Hi Jonathan,

Just a small issue under CoreGraphics Intro's image about the coordinate system.
It states that "the origin is in the upper-right-corner" but it should say "upper-left-corner".

Cheers,
Adam

[jrasmusson]

Thank you so much for pointing that out Adam! Don't know how I missed that. Fixed and pushed.

Cheers and happy programming!