rename plan to offer
Merge pull request #22 from lluis/rename_plan_to_offer

rename plan to offer
Change Paymill::API_BASE to api.paymill.com
Merge branch 'master' of github.com:dkd/paymill-ruby
Test against 1.9.2, 1.9.3, 2.0.0 and rbx-19
Remove rbx-19
Clean up
Update copyright information
Add documentation
Bump version for release
Add note about documentation
Add linebreak