migrate ChartsRealmDemo and bugfix

[liuxuan30]

1. upgrade ChartsRealmDemo to swift 4
2. fix CGAffineTransformInvert: singular matrix warning. data setter and zoom() order is reversed

[liuxuan30]

@petester42 I don't see Xcode warns me about @objc use when SWIFT_SWIFT3_OBJC_INFERENCE is on, and it works as usual without any warning throw out at run time. Does this mean we don't have to add @objc for classes such as BalloonMarker, XYMarkerView, RadarMarkerView, LargeValueFormatter, which are the only swift classes?

[pmairoldi]

The problem I had was that when using the new “minimize interface” that the objective-c code didn’t get acess to all the properties it needed. If you able to make stuff work without it go ahead.

[liuxuan30]

I'm not sure neither, as Xcode have no complain and works as usual.I clicked every realm demo chart and no crash at all. It seems all demo charts don't use marker at all. So @objc is not a must?

[pmairoldi]

If it works then whatever. We can revisit it if it stops working.

[pmairoldi]

Merge whenever you’re ready.