Automatic publish for snapshots by Travis

[tabdulradi]

Continuation for #26
Currently we have Travis setup, and Bintray setup.

Bintray only accepts non-snapshots, so we need

• OSS.JFrog account
• Modify SBT config to switch to JFrog if isSnapshot (which is provided by Sbt)
• Add encrypted keys to travis.yaml to be done automatically

[fedefernandez]

Hi, have you considered to publish the artifacts to oss.sonatype in order to have it available in maven central? this would avoid the extra resolvers.