Fix NameError on API

use @member instead of member
Add tests for Api::FeedController
Add tests for Api::FolderController
Add tests for Api::PinController
Add tests for ApiController
Merge branch 'fix_name_error' into add-tests-against-#10
`session.session_id` is gone at rails3

Use `session[:session_id]` instead of `session.session_id`.
Fix spec
Fix test

Folder#name is now attr_accessible attribute
Fix test

Pin#link, Pin#title is now attr_accessible attribute
Merge branch 'add-tests-against-#10' into rails-modern