emit_filter_spec is a huge (largely) untested hack

[antifuchs]

The string manipulation it does is fairly ad-hoc and terrible, and there is exactly one test for it (prompted by #4). I think this should be way better.

The most glaring missing feature that I can think of is that top-level "OR" groups need has :or => [x,y]; you can't even use `has [{:or => [x,y]}] without superfluous parens. There are probably more of these cases.

=> Needs a bit of a rewrite (-: