Revert "create an scaffold "avatar""

This reverts commit eec1a0038cb0ecc39b4c57218e35ff6120311d73.
scaffold "user"

* create an scaffold "user" with name and description
*
* $ rails g scaffold user name:string description:text

*
* alarm: No secret option provided to Rack::Session::Cookie
* Explanation:  This security warning was introduced in rack 1.4.2
released on rubygems.org on 6 Jan 2013. I've encountered this issue
after upgrading my existing app from rails 3.2.9 to 3.2.10 and bundle
update pulled in new rack 1.4.2. Related StackOverflow question to watch
http://stackoverflow.com/questions/10374871/no-secret-option-provided-to-racksessioncookie-warning
* Solution: The warning can be safely ignored by Rails users.

* $ rake db:migrate