Bug Fix: Issue 6 append and replace unexpected behavior if there's an & in task (even in quotes)

Using the cleaninput function, to escape &'s on certain actions.
Currently the actions needing escaped &'s are append, prepend and replace.
Other actions including add need unescaped &'s.

tests/t1600-append.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+
+test_description='basic append functionality
+
+Ensure we can append items successfully.
+'
+. ./test-lib.sh
+
+#
+# Set up the basic todo.txt
+#
+todo.sh add notice the daisies > /dev/null
+
+test_todo_session 'append usage' <<EOF
+>>> todo.sh append adf asdfa
+=== 1
+usage: todo.sh append ITEM# "TEXT TO APPEND"
+EOF
+
+test_todo_session 'basic append' <<EOF
+>>> todo.sh append 1 "smell the roses"
+1: notice the daisies smell the roses
+
+>>> todo.sh list
+1 notice the daisies smell the roses
+--
+TODO: 1 of 1 tasks shown from $HOME/todo.txt
+EOF
+
+test_todo_session 'basic append with &' <<EOF
+>>> todo.sh append 1 "see the wasps & bees"
+1: notice the daisies smell the roses see the wasps & bees
+
+>>> todo.sh list
+1 notice the daisies smell the roses see the wasps & bees
+--
+TODO: 1 of 1 tasks shown from $HOME/todo.txt
+EOF
+
+
+test_todo_session 'append error' << EOF
+>>> todo.sh append 10 "hej!"
+=== 1
+10: No such todo.
+EOF
+
+test_done