Re-think #463?

In #463, we changed the API for initializing a `CookbookSource`. In refactoring #363, a LOT of stuff was broken as a result. Can we revert https://github.com/RiotGames/berkshelf/commit/a4a40057f788ae8bf788d6c5dee7d2b99dae3dae and instead use the already-provided `options` hash for `:berskfile`?

1. It feels very messy to require another object in the initializer
2. It **requires** that a cookbook source is attached to a berksfile, which isn't always the case
3. It doesn't make sense - if I'm creating a "thing" the first "thing" I pass in should be that thing's name, not it's originating source. I wouldn't say `Seth.new(@hospital, "Seth")`

/cc @fnichol @schisamo @jtimberman and @reset because I know this was for TK stuff, but can we please think of a non-API breaking way :smile: