Make coverage task execute unit specs, even if already run.
Make coverage task execute unit specs, even if already run.

Rake::Task['spec:unit'].invoke is a no-op if the specs have already been
run, which is the case when, e.g. 'rake ci' is invoked.  Use #execute
instead to force specs to run whenever metrics:coverage is run.

zaidan/devtools,mvz/devtools,mbj/devtools,backus/devtools