hostname is optional

Setting the hostname is part of the pre-ansible install instructions, so
it is really only useful here to change the hostname. Changing the
hostname probably doesn't happen often and is simple enough without
ansible, so meh.

group_vars/all

@@ -9,8 +9,6 @@ dotfiles:
     url: git@github.com:pigmonkey/dotfiles.git
     rcup_flags: -x README.md
 
-hostname: nous
-
 aur:
     dir: aur
     packages:

roles/base/tasks/main.yml

@@ -7,6 +7,7 @@
 
 - name: Set the hostname
   hostname: name={{ hostname }}
+  when: hostname is defined
 
 - include: shell.yml
 - include: user.yml