added required fields to `pom.xml`.
added plugins for javadoc and sources JARs.
updated `.travis.yml` only test develop + master branches.
added deployment settings for sonatype snapshot repository.
Merge branch 'feature/prep-for-snapshot-releases' into develop

* feature/prep-for-snapshot-releases:
  added deployment settings for sonatype snapshot repository.
  updated `.travis.yml` only test develop + master branches.
  added plugins for javadoc and sources JARs.
  added required fields to `pom.xml`.