:grant_type instead of :type and client_credentials instead of client_cred for get_app_access_token_info

Complying with Facebook documentation (https://developers.facebook.com/docs/howtos/login/login-as-app/), app login flow should use 'grant_type' (not 'type') parameter and should request 'client_credentials'
fix result == nil when no pictures are retrieved from Facebook
Merge branch 'master' of git://github.com/miv/koala into app-token
Fix tests
Fix specs
Merge branch 'master' into app-token
Merge branch 'master' of git://github.com/ifeelgoods/koala into nil-array
Test for handling nils in get_picture
update changelog
Merge branch '2.0.0' of github.com:arsduo/koala into 2.0.0

Conflicts:
	spec/support/graph_api_shared_examples.rb