Version 0.2.11

* Added security options to nginx.conf.erb:

```
more_clear_headers 'Server';
more_clear_headers 'X-Powered-By';
more_clear_headers 'X-Runtime';
```

* Updated 'mysql' from '5.5.2' to '5.6.1'

* Removed setting of the version for cookbook 'serverdensity'
  as it raises error while running "berks update"
```
The cookbook downloaded for serverdensity (= 2.0.0) did not satisfy the constraint.
```