This should get things up to date for other pull requests so CI can properly verify tests and other fun stuff.
Updates Aegir to version 18.
Fixes lint and package scripts as a result of the update
Moves circleci to version 2, version 1 goes away on the 15th.
Removes yarn.lock. It was making Travis unhappy and seems unnecessary to have both.
Removes node 6 from Travis. The latest Aegir has code not compatible with node 6 and node 6 ends maintenance next month, so it should be a reasonable change.
This should get things up to date for other pull requests so CI can properly verify tests and other fun stuff.