Backbone: call initial Todos fetch with reset

If you want to smartly update the contents of a Collection, adding new models,
removing missing ones, and merging those already present, you now call set
(previously named "update"), a similar operation to calling set on a Model. This
is now the default when you call fetch on a collection. To get the old behavior,
pass {reset: true}.

In you code you use listener to 'reset' event. So you should pass {reset: true}
to get what you want.
Merge branch 'pr/871' into gh-pages

Close #871