Migrate CircleCI to a 2.0 configuration

[Arcanemagus]

CircleCI will be removing support for 1.0 configurations as of 2018-08-31. This is one of the repositories within this organization that is currently still configured to use a 1.0 configuration and needs to be migrated to the 2.0 format.

An automated translation can be found here, however it is likely that a better method would be to follow the Workflow based example from AtomLinter/atom-minimap-linter.