migrate to new structure which consists of only 2 tables
Modify 2 models
Make simpler (using only 2 models)
Enable to modify registered attendance
These should be included in previous commit
Use nil as default
delete unneed files about migration
Enable to add plans into an existed event
integrate forms to form.html.erb

Also sanitize previously registered plans correctly
Add an empty .travis.yml
Merge pull request #1 from kizashi1122/use-travis-ci

Use travis ci