Add 'gsu' alias for updating git submodules

Updates and initializes submodules recursively

aliases/available/git.aliases.bash

@@ -12,6 +12,7 @@ alias get='git'
 alias gst='git status'
 alias gs='git status'
 alias gss='git status -s'
+alias gsu='git submodule update --init --recursive'
 alias gl='git pull'
 alias gpr='git pull --rebase'
 alias gpp='git pull && git push'