add install
Update readme for installing
Merge with stable (expa)
Log rotate for app logs

- create config /etc/logrotate.d/dokku-app
- logrotate configs /etc/logrotate.d/dokku-app.d/*
- create deafault logrotate config in /etc/logrotate.d/dokku-app.d/<APP>
  rotating /var/log/dokku/<APP>/*log
update readme, pre-delete hook for logrotate cleanning
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minor readme