[#44] Add API to disable tap-to-dismiss

[marcuswu0814]

Hi @rnystrom, this PR implement the #44.

• Add a delegate method to check allow tap to dismiss. (If no delegate, default can be tap dismiss)
• Add a delegate property for some use case, for example, when wrapped the delegate pattern to Delegate Proxy with RxSwift.

If there have any suggestions or concerns, please let me know. 😃 Thanks.

[marcuswu0814]

Hi @BasThomas, could you help to review this PR and merge it? 🙏

[rizwankce]

LGTM :) @marcuswu0814 I don't have the write access to this repo though Im in the GItHawk org group