Improve aws-scala-sbt template

[NomadBlacky]

What did you implement:

Closes #XXXXX

• Improve aws-scala-sbt template.

How did you implement it:

• Specify sbt version by build.properties.
  • sbt launcher is able to download specific version and execute it.
  • Able to specify sbt version by build.properties.
• Bump up Scala version to 2.12.6
• Bump up library dependencies.

How can we verify it:

$ sls create -t aws-scala-sbt -p sls-scala
$ cd sls-scala
$ sbt sbtVersion # Please check the display of `1.1.6`
$ sbt scalaVersion # Please check the display of `2.12.6`
$ sbt assembly
$ sls deploy
$ sls invoke -f hello

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[horike37]

@NomadBlacky
Works great 👍 Thank you for your contribution!
merging...