Bump versions.
Avoid deprecated `error` in CompilationUnit.

`unit.reporter` simply forwards to `global.reporter`,
so use that one instead. Use `typer.context.error`
where silent mode should be respected (i.e., during type checking).
Merge pull request #8 from adriaanm/master

Use context for error reporting.
Bump versions
Avoid deprecation/feature warnings

This commit adds -deprecation and -feature to scalacOptions and fix source code to avoid deprecation/feature warnings.
Since scala/scala-continuations#8 is already working on the usages of deprecated CompilationUnit, this commit does not fix them.
Use reporter.warning instead of deprecated unit.warning
Update sbt to 0.13.6