created app.json
add deploy button

see:
http://d.hatena.ne.jp/naoya/20140809/1407556488
https://github.com/naoya/md2inao
fix: app.json caused error

There was a problem with the app.json file found at "https://github.com/DQNEO/yourdotfiles/tree/heroku_button":
name is too long (maximum is 30 characters)
Merge pull request #1 from DQNEO/heroku_button

add Heroku button