Port ios-charts to OS X.

[pixelspark]

This commit adds a thin UIKit/Cocoa abstraction layer (Util/ChartsPlatform.swift). It also adds an OS X demo application.

With reference to #43

[pixelspark]

Ah, I might have inadvertently set the target platform for the 'Charts-iOS' target to OSX. Simply changing this back to iOS should fix the test.

[pmairoldi]

Great work! Looks good to me. I will merge this into a separate branch so that we can work on it to make sure everything is good before it goes into a release.

[pmairoldi]

OS X work can be found here

[danielgindi]

Great!
It's amazing that this is actually happening. I love open source :-)

[pixelspark]

Glad I could help out & good to see this is being adopted by the project!

I have been testing the charts in an OSX app and have not seen any major issues. Line, bar, radar, pie and scatter plots seem to work fine. Some things to work on:

• Some of the default fonts are a bit small on OSX. The easy fix is to use [NSUIFont systemFontOfSize:] with a different size for OSX. Even better would be to integrate with Dynamic Type on iOS (don't know if it exists at all on OSX?).
• The gestures need some work. A pinch gesture recognizer is most notably missing in OSX (but can probably be implemented with a custom gesture recognizer and a bit of work).
• Animation of charts is smooth with my 'fake' timer-based implementation of CADisplayLink. We may want to look into CVDisplayLink on OS X for a 'real' implementation.

[danielgindi]

No Dynamic Type in OSX...

[danielgindi]

I'm not too much worried about defaults - those could be adjusted later... Let's get the real problems fixed first :-)

[danielgindi]

It turns out that there's a NSMagnificationGestureRecognizer :-)
I'm creating the bridge now...

[danielgindi]

There are issues with "nsuiGestureRecognizerShouldBegin" though - as it is not really mapped to anything.