Gulp > Add postship

[rafaelstz]

Add postship task from Casper, it will:

• added gulp task to extend Lyra release automation
• will draft the release for you
• will get the user facing commits from changelog
• runs after yarn ship (postship)
• full automation with env variables is possible

[minimaluminium]

Thanks for the PR! But we don't do releases on Lyra at the moment.