Move dictionaries to i18n

I'm not sure I see the "hidden" contexts you refer to unless you mean the parameters.  I see

- class
- method
- 2 params (one of which is an options hash, which can be thought of an N params)
- expected
- actual

I can't see it getting any more straightforward than that.  To me the current version is clearer because all 5 things are in each spec, making each spec live and readable on its own.  Separating it only seems to make the spec more confusing, to me at least.