Add customization options.

Allow setting:
- Overlay background color
- Overlay success color
- Delay before overlay slides out on sucess
- Duration for the overlay slide-in/-out
Respect 'prefersStatusBarHidden' of the root view controller
Add tint color to gestures / touch indicator
Merge branch 'master' of https://github.com/equinux/Flow into equinux-master
Bug fix and UX.
Merge branch 'equinux-master'
Release 1.4.0.