* Add scalafix plugin for jdk 9.
* Add command alias sortImports.
* Excludes some sources from SortImports.
* Update SortImports to 0.4.0
* Sort imports with `sortImports` command.
* scalafix ExplicitNonNullaryApply prepare
+ Temporarily use com.sandinh:sbt-scalafix because scalacenter/scalafix#1098
+ Add ExplicitNonNullaryApply rule to .scalafix.conf
+ Manually fix a NonNullaryApply case in DeathWatchSpec that cause
`fixall` fail because ExplicitNonNullaryApply rule incorrectly rewrite
`context unbecome` to `context unbecome()` instead of `context.unbecome()`
* scalafix ExplicitNonNullaryApply
fix by enabling only ExplicitNonNullaryApply rule in .scalafix.conf then:
```
% sbt -Dakka.build.scalaVersion=2.13.1
> fixall
```
* scalafmtAll
* Revert to ch.epfl.scala:sbt-scalafix
Co-authored-by: Bùi Việt Thành <thanhbv@sandinh.net>
