Improvement: adopt shouldShowRequestPermissionRationale

[stari4ek]

• https://developer.android.com/training/permissions/requesting.html

if user denied permissions already - we have a chance to show explanation UI.
And this is the way to honor "don't ask again".

[stari4ek]

Hmm. Probably there is no need to integrate it to the lib.
it's possible to use PermissionUtils.toPermissions with shouldShowRequestPermissionRationale on it, and go with request after if needed.

Great lib design, btw!