removed redundant skip_before_action
refactoring authenticate_controller related, ready for cookie sign_in
cookie login is now available.
cookie test added.
added a migration: account_activations, provider_tokens is merged into users, now users has_many activation_tickets
refactored authentication codes using services,
some models are removed.
migration file (20141012150938_merge_account_activations_and_provider_tokens_into_users.rb) is modified.

all tests are passing
rename activation_tickets to invitations
test: authenticates::activate_user_service
test: authenticates::create_invitation_service
test: authenticates::kakao_sign_in_service
test: authenticates::phone_number_sign_in_service
add base service
test: invitation model
activated -> activated?
user who is signing in with phone number should be regarded as activated.
signing out problem is also fixed.
test: authenticates::cookies_sign_in_service
test: authenticates::user_session
authenticates::user_storage is base of authenticates::user_session, authenticates::user_cookies
test: authenticates::user_session, authenticates::user_cookies
Merge branch 'develop' of github.com:DonutWorks/Ari into refactor/issue-268