Use more portable uname -n rather than hostname.

Fixes #312

Author: bobthecow

functions/fish_prompt.fish

@@ -690,7 +690,7 @@ end
 # Polyfill for fish < 2.5.0
 if not type -q prompt_hostname
     if not set -q __bobthefish_prompt_hostname
-        set -g __bobthefish_prompt_hostname (hostname | string replace -r '\..*' '')
+        set -g __bobthefish_prompt_hostname (uname -n | string replace -r '\..*' '')
     end
 
     function prompt_hostname

functions/fish_title.fish

@@ -8,7 +8,7 @@ function __bobthefish_title_user -S -d 'Display actual user if different from $d
     if [ "$theme_title_display_user" = 'yes' ]
         if [ "$USER" != "$default_user" -o -n "$SSH_CLIENT" ]
             set -l IFS .
-            hostname | read -l hostname __
+            uname -n | read -l hostname __
             echo -ns (whoami) '@' $hostname ' '
         end
     end