Initial rubocop support for attributes/*.rb

Keeping in accordance with the other projects, adding a few standard
settings for rubocop. Dont check line lengths and dont suggest word arrays
for attributes files.

Addresses: blueprint rubocop-for-identity
Change-Id: I68728d2b9f73362fb4333c34dd6ed611efb4e7af
Merge "Initial rubocop support for attributes/*.rb"