Make compatible with Lodash v4

[marfire]

It would be nice if backbone.stickit was compatible with Lodash version 4.

For example, right now it's using the context argument (i.e. the this binding) in some places (like here), support for which has been removed from Lodash v4.

[akre54]

Really wish John-David hadn't broken the interface for these.

I'll happily accept a pull that fixes anywhere we're using the third arg.

[bazineta]

#308 should, I believe, address all lodash v4 compatibility issues. In addition to the third arg changes, invoke and contains were also affected.