update Scala.js and sbt versions (on 2.13 release branch)

[SethTisue]

@rickynils hopefully this will permit publishing 1.14.0 for Scala.js
on Scala 2.13.0-M5?

[ashawley]

LGTM

[non]

[error] /Users/erik/w/scalacheck/js/src/main/scala/org/scalacheck/Platform.scala:25:31: object TestUtils in package testinterface is deprecated (since 0.6.25): Use scala.scalajs.reflect.Reflect (JS-only) or https://github.com/portable-scala/portable-scala-reflect (portable) instead.
[error]     org.scalajs.testinterface.TestUtils.loadModule(name, loader)
[error]                               ^
[error] /Users/erik/w/scalacheck/js/src/main/scala/org/scalacheck/Platform.scala:28:31: object TestUtils in package testinterface is deprecated (since 0.6.25): Use scala.scalajs.reflect.Reflect (JS-only) or https://github.com/portable-scala/portable-scala-reflect (portable) instead.
[error]     org.scalajs.testinterface.TestUtils.newInstance(name, loader, paramTypes)(args)
[error]                               ^
[error] two errors found
[info] Done compiling.
[error] (js / Compile / compileIncremental) Compilation failed
[error] Total time: 32 s, completed Oct 14, 2018 4:53:54 PM

I'll try to figure out how to either update the code to fix this, or to disable the deprecation warning (for now).

[rickynils]

@non I tried disabling the deprecation warning (first for the js project, then generally), but did not succeed. It kept error out on the deprecations anyway.

[SethTisue]

I'll try to figure out how to either update the code to fix this

two examples of how it was done in other test frameworks (cc @sjrd)

• Use portable-scala-reflect instead of the deprecated TestUtils. com-lihaoyi/utest#178
• Fix #27: Replace TestUtils with portable-scala-reflect. monix/minitest#28

it doesn't look super hard, but it's not trivial either, so in the interest of getting the M5 publishing done, I think for now it's fine to disable the deprecation warning. I'll look at that next.

[SethTisue]

okay, I pushed a revised commit that disables -Xfatal-warnings in the Scala.js build only

I also downgraded sbt from 1.2.4 to 1.2.3 since I was hitting "different extra api hashes for no traits" (sbt/zinc#606)

[rickynils]

@SethTisue Thanks! I have now finally released the M5 build for the JS project too.

[SethTisue]

sweet, thank you Rickard!