This is travis helper to run particular work only once in matrix.

This is workaround for: travis-ci/travis-ci#929

The main goal of this script to have single publishing when build have several jobs.

• If other jobs will start late, can be global build timeout. (Think of passing leader role to others)
• More flexible leader defenition (In Matrix not all jobs can publish)
• Have several leaders, according to flavours (E.g. if in Matrix slices responsible for platform)