Upgrade build gradle

[tamtps]

Issue description

I have issue when add compile 'io.card:android-sdk:5.5.1' is "Multiple dex files define Lio/card/payment/CardIOActivity;"
I think this issue by conflict build tool gradle, please update gradle to latest version in card.id SDK.

[kahakai]

It's probably not because of Gradle as I'm using this library with Gradle 4.7 and Android Gradle Plugin 3.2.0-alpha15 without any problems.