Changes to OAuth2 authentication JSON output

[xelwarto]

Example code located on the Google developers site for Ruby (https://developers.google.com/api-client-library/ruby/auth/web-app) utilizes the JSON output of the authentication information in a stored session for creating the OAuth2 client. While this works correctly for the first fetch of the access token, the JSON output does not provide adequate information regarding the expiration of the access token. With out the expiration information it is impossible to track and test for an expired access token in subsequent API executions. The changes in this PR add the expires_in and issued_at parameters to the JSON output which allows the client to properly track and verify if the access token has expired.

Additionally, while testing the creation of an OAuth2 client using the JSON output I came across an exception with how the authorization URI was being created. The following error was reported:

/usr/local/lib/ruby/gems/2.1.0/gems/addressable-2.3.6/lib/addressable/uri.rb:1579:in `sort!': comparison of Array with Array failed (ArgumentError)
    from /usr/local/lib/ruby/gems/2.1.0/gems/addressable-2.3.6/lib/addressable/uri.rb:1579:in `query_values='
    from /usr/local/lib/ruby/gems/2.1.0/gems/signet-0.6.0/lib/signet/oauth_2.rb:152:in `generate_authorization_uri'
    from /usr/local/lib/ruby/gems/2.1.0/gems/signet-0.6.0/lib/signet/oauth_2/client.rb:263:in `authorization_uri'
    from /usr/local/lib/ruby/gems/2.1.0/gems/signet-0.6.0/lib/signet/oauth_2/client.rb:853:in `to_json'

The issue was the result of mismatched hash key types ... the resulting merge of the query_values hash had a mix of both Symbol and String key types. This PR includes changes to normalize the query_values hash before the merge.

[xelwarto]

The Signet library is failing to pass build due to changes to the JWT library. The following PR: jwt/ruby-jwt#45 implements claim expiration enforcement and since the Signet test specs include an expired token the build fails with an exception ...

Failure/Error: expect(@client.decoded_id_token).to eq ({
     JWT::ExpiredSignature:
       Signature has expired
     # ./lib/signet/oauth_2/client.rb:694:in `decoded_id_token'

[TheRoyalTnetennba]

Closing due to inactivity. Feel free to ping to-reopen