update rake and rdoc dependencies so rake can run.

I was getting:

    /Users/mike.frawley/.rbenv/versions/1.9.2-p290/lib/ruby/gems/1.9.1/gems/bundler-1.2.3/lib/bundler/rubygems_integration.rb:223:in `block in replace_bin_path': can't find executable rake (Gem::Exception)

with the old version of rake installed when running as `bundle exec rake`
show instructions on how to copy config.yml file in rake task
Add google v3 url signing for business accounts

Instead of just passing along your key as a query param, you must pass
along a SHA1 base64 encoded version of your query url as a `signature`
parameter now.  This logic only runs if you instantiate the geocoder
with the secret key and client id.

I needed to modify the google constructor to take api key and client_id,
and I also made the api key optional (which it already was, you just
needed to explicitly call it like `new(nil)`.
https://developers.google.com/maps/documentation/business/webservices#digital_signatures

Added a basic test.
Merge pull request #30 from ratbeard/google-auth

Google auth