Major upgrade: 2.0 release of the Payment Highway Android SDK

A whole new API for easier, more refined, more customizable integration to your app!

Highlights:

• new demo application https://github.com/PaymentHighway/paymenthighway-android-sdk/tree/master/demo
• customize the theme https://github.com/PaymentHighway/paymenthighway-android-sdk/tree/master/demo#how-customize-appearence-of-the-payment-highway-ui-elements
• new, more comprehensive API documentation https://paymenthighway.github.io/paymenthighway-android-sdk/