Updated Cake composer installation path.

Fixes issue with composer no longer being able to install Cake core via PEAR.
Changes vagrant VM name to prevent possible collisions with existing boxes.

Also removes emacs install, since that takes a good five minutes during initial provisioning and nobody needs it for this.
Adjusts composer packages for actual use.
Saves a normalized puphpet base path for the VM to use internally.
Replace the keygen script with latest.

Ref: https://github.com/puphpet/puphpet/blob/master/src/Puphpet/MainBundle/Resources/views/manifest/puphpet/shell/ssh-keygen.sh
Keep the puphpet/files/dot/ssh/ folder around.
Merge pull request #1 from beporter/f/composer-fixes

F/composer fixes