Always execute local karma
Always execute local karma

This ensure the dev will run the version specified in the package.json.
Besides, makes the rake task work as all rails tests, allowing you to
pass a RAILS_ENV.

Matt-Yorkley/openfoodnetwork,Em-AK/openfoodnetwork,KateDavis/openfoodnetwork,lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork,openfoodfoundation/openfoodnetwork,oeoeaio/openfoodnetwork,Matt-Yorkley/openfoodnetwork,KateDavis/openfoodnetwork,mkllnk/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Em-AK/openfoodnetwork,openfoodfoundation/openfoodnetwork,mkllnk/openfoodnetwork,Em-AK/openfoodnetwork,mkllnk/openfoodnetwork,Matt-Yorkley/openfoodnetwork,KateDavis/openfoodnetwork,oeoeaio/openfoodnetwork,mkllnk/openfoodnetwork,Em-AK/openfoodnetwork,KateDavis/openfoodnetwork,oeoeaio/openfoodnetwork,openfoodfoundation/openfoodnetwork,openfoodfoundation/openfoodnetwork,oeoeaio/openfoodnetwork