conditionally define t()

if user has enabled the todo plugin, skip defining the 'one thing'
todo function t().

plugins/available/base.plugin.bash

@@ -151,18 +151,20 @@ usage ()
     fi
 }
 
-t ()
-{
-    about 'one thing todo'
-    param 'if not set, display todo item'
-    param '1: todo text'
-    group 'base'
-	if [[ "$*" == "" ]] ; then
-	    cat ~/.t
-	else
-	    echo "$*" > ~/.t
-	fi
-}
+if [ ! -e $BASH_IT/plugins/enabled/todo.plugin.bash ]; then
+# if user has installed todo plugin, skip this...
+    t ()
+    {
+        about 'one thing todo'
+        param 'if not set, display todo item'
+        param '1: todo text'
+        if [[ "$*" == "" ]] ; then
+            cat ~/.t
+        else
+            echo "$*" > ~/.t
+        fi
+    }
+fi
 
 command_exists ()
 {