Update build file to use springio-platform plugin
Fixes
Update to gradle 1.12
Implement a fork/join pool for doing arbitrary asynchronous task execution and coalescing the result into a Composable.
Fix compilation error on JDK <8
Update springio-platform-plugin version and repo reference.
Update the configuration of the Spring IO plugin

 - Update the version to 0.0.3.RELEASE
 - Apply the plugin to all projects
 - Add a dependency on the platform's versions

 With these changes ./gradlew clean springIoCheck -PJDK8_HOME=… builds
 cleanly
Tweak ForkJoinPool to handle joining tasks into a Promise differently than forking tasks using a Stream
Tweak how results are collected.