1. Implement selector for button background #4
Attributes changes
- replaced `cpb_colorComplete` with `cpb_selectorComplete`
- replaced `cpb_colorError` with `cpb_selectorError`
- replaced `cpb_colorIdle` with `cpb_selectorIdle`
- removed `cpb_colorDisabled` (now you can use above selector)
2. Added Custom Selector Sample