chore(copyright): Update to grunt-copyright v0.2.0
chore(copyright): Update to grunt-copyright v0.2.0

When doing an `npm install` using node v0.12, it complains since grunt-copyright
v0.1 has a `"node": "0.10.x"` in it's `engines` section. v0.2 has been updated
to be `"node": ">= 0.10.0"` which is satisfied with either v0.10 or v0.12.

eoger/fxa-auth-db-mem,chilts/fxa-auth-db-mem,mozilla/fxa-auth-db-mem