Sort case insensitively on todo texts

test/data/SorterTest1-result.txt

-First
+first
 (A) Foo
 2014-06-14 Last

test/data/SorterTest1.txt

 (A) Foo
 2014-06-14 Last
-First
+first

test/test_sort_command.py

@@ -33,14 +33,14 @@ class SortCommandTest(CommandTest):
         command.execute()
 
         self.assertEqual(self.todolist.print_todos(),
-                         "First\n(A) Foo\n2014-06-14 Last")
+                         "first\n(A) Foo\n2014-06-14 Last")
 
     def test_sort2(self):
         command = SortCommand([], self.todolist, self.out, self.error)
         command.execute()
 
         self.assertEqual(self.todolist.print_todos(),
-                         "(A) Foo\n2014-06-14 Last\nFirst")
+                         "(A) Foo\n2014-06-14 Last\nfirst")
 
     def test_sort3(self):
         """ Check that order does not influence the UID of a todo. """

topydo/lib/Sorter.py

@@ -57,7 +57,7 @@ def get_field_function(p_field):
     elif p_field == 'project' or p_field == 'projects':
         result = lambda a: sorted([c.lower() for c in a.projects()])
     elif p_field == 'text':
-        result = lambda a: a.text()
+        result = lambda a: a.text().lower()
     else:
         # try to find the corresponding tag
         # when a tag is not present, push it to the end of the list by giving