generator-bat

refactor(coffeescript2): move `'use strict'` declarations to their outermost, file level

Paving the way for a smooth(er) transition to `coffeescript@>=2`.

This change virtually implies having to include `jshint`'s relaxing `validthis` option into your `coffee-jshint` config in order to avoid warnings about the
`extend()` function definition that `coffeescript` injects for every `extend`-ed `class`.

That is, at least for as long as we're stuck with `coffeescript@ < 2`.
After we've crossed, `validthis` can be unset again.

As to why this change is needed, see:

    https://www.nczonline.net/blog/2016/10/the-ecmascript-2016-change-you-probably-dont-know/

And while this is not a "breaking change" per se, newly generated `bat:model`s, -`:collection`s and `:view`s will come to differ from any you generated before
this change.  So you may want to change existing files in similar fashion, before you consider transitioning your existing app to `coffeescript@ >= 2` too.