Add .overcommit.yml file

Change-Id: I4d9b38b90a73f15a46fe1aeaa5bbd29e049bf603
Reviewed-on: http://gerrit.causes.com/35593
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>
Use subject instead of let(:subject)

Correct a simple oversight. Using `subject` is more idiomatic.

Change-Id: I33e419946c4598d0e28d4bdb30f4ef0a1d57e8b1
Reviewed-on: http://gerrit.causes.com/35594
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>