Automate releasing a version of Bastion

[KPull]

We currently do the following when releasing a new version of Bastion:

• Merge the develop branch into master branch.
• Set the POM file's version to the next release version number.
• Run mvn deploy -Prelease.
• Commit.
• Tag the current commit on master for the version we're releasing.
• Merge master into develop.
• Set the POM file's version to the next SNAPSHOT version.
• Commit.
• Push master, develop and the new tag.

We need to automate/script this so that we can configure Travis to run the whole process by itself.