Anchor customisation

Add possibility to customise anchor color

Fix code style issue

1.0.4

Fix protocol conformance

Extend SliderController with SliderControlling protocol

Xcode 9 and Swift 4.0

Make SliderController compatible with projects in Swift 4.0.

Improve drawing slider

Improve drawing mechanism inside drawImage(color:) function in Slider class.

Initial release

1.0.0