Implement essential java.io.Readers
Implement essential java.io.Writers
Implement java.io.ByteArrayOutputStream
Merge pull request #925 from gzm0/java-io

Implement essential classes of java.io
Create a jsDependencyManifest task. Integrate with ExternalCompile
Implement java.util.zip.ZipInputStream
Remove unused code reading source maps
Refactor tools.json to abstract backend-specifics into a single file
Cross-build Scala.js tools
Implement virtual file systems for Node.js
Link HelloWorld in JavaScript for testing