When using embed: :ids ; embed_in_root: true, and serializing multiple objects,
only the associated objects of the last object in the collection will actually
show up in the serialized data.

For example, if you serialize a collection of two posts, each containing one or
more comments, only the comments of the last post show up. The reason is a
Hash#merge wich overwrites the array rather than appending to it.

This commit fixes this by merging the collection arrays, rather than the top-level
hashes.
Fixes a bug in the HasOne association where serializing twice in a row causes
an exception.
Add @options back into serializers to maintain the functionality of render :json as noted in the docs

This functionality used to exist in v0.8.1. This adds the ability to
pass other options that will be usable in the serializer via the
options accessor.

This works by adding an attr_accessor for options so it is available
and is set by the remaining options in the provided options hash during
initialization.
Merge pull request #453 from jasontruluck/master

Add @options back into serializers for passing custom options
Update Rubinius to 2.2.1
Alow rbx to fail
Ruby-head and fast_finish
Use jruby and rbx in Travis
Do not allo ruby-head failures
Serializers now inherit attributes and associations.
Merge pull request #451 from plexus/embed_in_root_merge

embed_in_root only returns the associated objects of a single instance
Split basic object and model array serialization tests
Move serialization tests to serialization_test.rb
Stub out comments writer when needed
Merge pull request #468 from stas/attrs_and_assoc_inheritance

Serializers now inherit attributes and associations.
Remove explicit reference to self
Test association inheritance in serializers
Serializers now inherit root
Merge pull request #452 from plexus/has_one_each_serializer_fix

Using a HasOne association twice raises an exception (Undefined method `map')
Avoid unneeded logic