fixed colorize for OSX

exit -1 destroys a terminal, now returns -1
which doesn't return just a path, so awked out the last field

plugins/colorize/colorize.plugin.zsh

@@ -6,9 +6,9 @@
 alias colorize='colorize_via_pygmentize'
 
 colorize_via_pygmentize() {
-    if [ ! -x $(which pygmentize) ]; then
+    if [ ! -x $(which pygmentize | awk ' { print $(NF) } ') ]; then
         echo package \'pygmentize\' is not installed!
-        exit -1
+        return -1
     fi
 
     if [ $# -eq 0 ]; then
@@ -25,4 +25,4 @@ colorize_via_pygmentize() {
             pygmentize -g "$FNAME"
         fi
     done
-}
+}