More todos

TODO.txt

@@ -1,4 +1,5 @@
 Write Repeat tests
+Create a ReaderAt[Datum any] interface and combine Cursor with State
 Think about not requiring so much Pos() when making messages
 Rename Seq2 to Seq
 Document Seq

parser_test.go

@@ -143,4 +143,6 @@ func TestRepeat(t *testing.T) {
 	t.Run("succeeds when number of successes is greater than minCount", Todo)
 	t.Run("consumes iff at least one application consumes", Todo)
 	t.Run("fails on error", Todo)
+	t.Run("position is unchanged on failure", Todo)
+	t.Run("position follows last success on overall success", Todo)
 }