Better attribute support

Can now do things like:

attributes.class << 'foo'
attributes.class.ensure('bar')
attributes.class.any_array_method(…)
Refactor `find_bindings` to be recursive

Allows the nested data structure to be built much more directly. Code
simplification FTW.
Use different method of removal in `match` so bindings are not refound
Merge branch 'master' into 0.9-dev

Conflicts:
	pakyow-presenter/lib/presenter/view.rb