Make params argument optional

[kentcdodds]

There is a use case where I don't want to include query parameters. Currently, I am forced to do: DS.findAll('user', {}). I would prefer to leave off the object if I don't have any query params. This isn't a really big deal, except it looks like the request is getting sent with query=%7B%7D (aka query={}) which is not desirable or necessary in this case. I would much rather angular-data be smart enough to allow me to not have any query param at all if I don't specify params.

[jmdobry]

There are three lines in src/adapters/http.js that would need to be reworked to fix this (findAll, updateAll, destroyAll).