Simplified release process

[ghost]

There's currently too many steps required for releasing Athena and its plugins. Currently the process involves the following:

• Create a local git tag and push it to the remote
• Update the CHANGELOG.md file with a diff manually generated
• Update plugins/base/version.txt (Athena project) or version.txt (any plugin project)
• Update the respective brew tap definition
• Update the respective Debian package in Launchpad

This process is slow, error prone and can definitely be simplified.