formatted grunt completion and used helper function

completion/available/grunt.completion.bash

@@ -41,10 +41,13 @@
 # eval "$(grunt --completion=bash)"
 
 # Search the current directory and all parent directories for a gruntfile.
+
+if _command_exists grunt
+then
     function _grunt_gruntfile() {
         local curpath="$PWD"
         while [[ "$curpath" ]]; do
-    for gruntfile in "$curpath/"{G,g}runtfile.{js,coffee}; do
+            for gruntfile in "$curpath/"{G,g}runtfile{.js,.coffee,}; do
                 if [[ -e "$gruntfile" ]]; then
                     echo "$gruntfile"
                     return
@@ -73,3 +76,4 @@ function _grunt_completions() {
     }
 
     complete -o default -F _grunt_completions grunt
+fi