Allow for passing templates on view initialization. Fixes #75

Issue mentioned here https://github.com/AmpersandJS/ampersand-view/issues/75
What I'm only not quite sure is whether we should make it prior or after `initialize` function itself.
If you just add 'template' to https://github.com/kamilogorek/ampersand-view/blob/feature/initialization-template/ampersand-view.js#L83 it will have the same effect I think.