Set up Travis to deploy tagged commits to Github Releases

[RohanNagar]

Step 1 in the containerization and deployment process.

Travis should continue to build and report status as normal, but additionally on tagged commits (commits that are intended to be a new version of Thunder), the application jar should be added to the release.

This is more of a consolidation into Github as a platform, and not relying on AWS S3 to hold our releases. We should use JitPack going forward for including the api and client modules in other projects, instead of relying on S3. This will improve the development process for Lightning, as AWS keys will no longer be needed to build.

[RohanNagar]

Made some changes to .travis.yml in 9e80dda.

However, this is still broken. The application jar is not published to Github releases on a tagged commit because Travis currently only does a test, not a package.

We should update the script to run a full mvn clean package.

Also, for easier release pushes we need to change the maven-release-plugin to only install and not attempt to publish the artifacts.

[RohanNagar]

We need to update the branch restriction on Travis to include this regex: ^[v](\d+\.)?(\d+\.)?(\d+)$. This will match the format of tagged commits, allowing Travis to build them