Set initial version at 0.0.1-SNAPSHOT

Per Semantic Versioning 2.0.0, with the deviation that we use a dash (-)
instead of a dot (.) to delimit the SNAPSHOT qualifier to conform to
widely used Maven artifact versioning practices.

See http://semver.org
Add CONTRIBUTING.md with link to ClaHub agreement
Configure publication to Bintray

See:
 - https://github.com/bintray/gradle-bintray-plugin
 - http://www.gradle.org/docs/current/userguide/publishing_maven.html