Upgrade Gradle Wrapper Version

[manusa]

Description

Update Gradle Wrapper version to latest

https://travis-ci.org/manusa/isotope-mail/builds/596436887

Relates to

• marcnuri-demo/spring-mockmvc-test#1
• marcnuri-demo/java8-streams-list-to-map#1
• marcnuri-demo/spring-mongo-sequences#1
• marcnuri-demo/angularboot#1