Change Dokku public key after setup
So when setting up a Dokku instance from the default web interface, I mistakenly pasted a PuttyGen formatted public key. Dokku doesn't do any checking here and I couldn't figure out why I couldn't log in to the box with my private key.
I eventually thought of the key format and checked /home/dokku/.ssh/authorized_keys and removed the ill formatted public key and replaced with the one PuttyGen tells you to use for openSSH.
There's a command line at the top that I believe Dokku places in authorizedkeys. I initially placed the good key on it's own line. While this passed the ssh test, git would return errors when trying to push:
```
$ git push dokku master
Enter passphrase for key '/c/Users/abc/.ssh/idrsa':
fatal: 'www' does not appear to be a git repository
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
```
Eventually remembered that the bad key started on the top line at the very end. Moving the key up to the end of the first line did the trick.