This change allows the Kotlin compiler to type check methods annotated with the
org.elasticsearch.common.Nullable annotation in Elasticsearch Java
APIs as described in: https://kotlinlang.org/docs/reference/java-interop.html#jsr-305-support.
(cherry picked from commit 0d0485ad9cf10e16b75b862b023b42827c375599)
hamcrest has some improvements in newer versions, like FileMatchers
that make assertions regarding file exists cleaner. This commit upgrades
to the latest version of hamcrest so we can start using new and improved
matchers.