If an model is gone from a POSTed association, null out its FK

On client update resource's association if someone modifies the
ResourceProxy's result Array (using shift for example) so that the
changed association list can be pushed to the server.
remove old client-side assoc delete testing code
update ResourceProxy tests for delete support changes
use CollectionProxy#delete for association removal
Merge remote-tracking branch 'origin/master' into remove_through_associations
use association.ids_reader to get the current ids
ignore multilevel associations when updating collection attributes

has_many through and habtb
make error unique for has_many vs habtm associaitons
make sure we can remove _all_ things from a collection
support rails 4.0 habtm reflection lookup
check for habtm relationships in rails 4.0
wrap array methods on ResourceProxy when they are first used
streamline is_collection_multilevel?

created has_many_type to return 'has_as_belongs_to_many', 'has_many
:through' or nil (not either of those two types) for the association in both the
Rails 4.0 and 4.1 cases.
not all reflections have a parent
Merge pull request #44 from att-cloud/remove_through_associations

Handle client side association collection removals. Fixes #15