[issue-225] Source and target java8

[bluesheeptoken]

Using java13 before the PR:

java -version # `openjdk version "13.0.2" 2020-01-14 `
sbt package
cd target/scala-2.11
unzip rediscala_2.11-1.9.0.jar
javap -verbose redis/util/CRC16.class | grep version # major version: 57

After the PR:

java -version # `openjdk version "13.0.2" 2020-01-14 `
sbt package
cd target/scala-2.11
unzip rediscala_2.11-1.9.0.jar
javap -verbose redis/util/CRC16.class | grep version # major version: 52

It has also been tested in production with our Java 8 backend.

Thanks for the project, we really appreciate it!

Should fix #225

[bluesheeptoken]

@etaty Sorry for pinging you again for the exact same issue :)

I have made this PR as this is probably the minimal line of code to make sure this is compatible with java8 +.

Let me know if there is anything I can do. Thanks

[coveralls]

Coverage decreased (-0.06%) to 90.386% when pulling c97ed37 on bluesheeptoken:fix-issue-225 into 5600b00 on etaty:master.