Ecrire::Railtie paths was not in the application's reload path.

The application's path did not include Ecrire's paths. Needed to add a
new initializer to take care of that. It's also necessary to add a
:before option because railtie freeze the paths before passing the paths
to ActiveSupport
Updated template which close #42
Modified helper method. Not sure I'm going to keep it like that.

It actually takes the global namespace PostsHelper and I think it's not
really useful to spend it for a single method. Anyway.. I'm going to
think about it.