[split] Move fishface theme to oh-my-fish/theme-fishface

https://github.com/oh-my-fish/theme-fishface

themes/fishface/README.md

-## FishFace
-
-Shows an ASCII fish which is blue or green when in a git repo.
-
-![fishface theme](https://f.cloud.github.com/assets/66143/1224622/ec9660d8-2750-11e3-9c96-cb7a5a69eada.png)

themes/fishface/fish_prompt.fish

-# name: FishFace
-
-function _git_branch_name
-  echo (command git symbolic-ref HEAD ^/dev/null | sed -e 's|^refs/heads/||')
-end
-
-function _is_git_dirty
-  echo (command git status -s --ignore-submodules=dirty ^/dev/null)
-end
-
-function fish_prompt
-  set -l blue (set_color -o blue)
-  set -l green (set_color -o green)
-
-  if [ (_git_branch_name) ]
-    echo -n -s "$green><(((\"> "
-  else
-    echo -n -s "$blue><(((\"> "
-  end
-end