MINOR: Update dependencies for 0.11

[ijuma]

Worth special mention:

1. Update Scala to 2.11.11 and 2.12.2
2. Update Gradle to 3.5
3. Update ZooKeeper to 3.4.10
4. Update reflections to 0.9.11, which:
   • Switches to jsr305 annotations with a provided scope
   • Updates Guava from 18 to 20
   • Updates javaassist from 3.18 to 3.21

There’s a separate PR for updating RocksDb, so
I didn’t include that here.

[enothereska]

Cool, LGTM

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/kafka-pr-jdk8-scala2.11/3018/
Test PASSed (JDK 8 and Scala 2.11).

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/kafka-pr-jdk7-scala2.10/3013/
Test PASSed (JDK 7 and Scala 2.10).

[ijuma]

Review by @hachikuji

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/kafka-pr-jdk8-scala2.12/3014/
Test PASSed (JDK 8 and Scala 2.12).

[hachikuji]

LGTM. Might be worth running one of the system tests just to make sure nothing breaks in the provisioning process.

[ijuma]

Passing system test: https://jenkins.confluent.io/view/All/job/system-test-kafka-branch-builder/845/