Configure snapshot publication to oso.jfrog.org

 - Introduce 'publishSnapshot' Gradle task; configure Travis to use it
 - Supply authentication credentials in encrypted form
 - Further configure Maven artifact publication and add new Artifactory
   publication configuration
 - Re-organize and document major sections of build script
Add basic project information to README

Including how to access the snapshots that are now being published
continuously.
Merge branch 'publish-snapshots'