Updated ashikawa-core to support graphs
Added Acceptance spec for graph bases relations
Added basic edge implementation
DocumentModelMapper: Added an Attribute class to represent mapped attributes
Updated Rspec to 3.1

This was done because I needed the `have_attributes` matcher
DocumentModelMapper: Extracted handling of references/embeds
Mapper: Add proxy for relations within a graph
Configuration: Added the graph to the config
Relation Proxy: Added actual implementation
DocumentMapper: Remove related attributes from document
Added EdgeCollection class
EdgeCollection: Added basic methods to access graph and connection
EdgeCollection: Add the edge definition to the graph

This will happen as soon as you include the Guacamole::EdgeCollection
module.
EdgeCollection: Added #neighbors method
EdgeCollection: Neighbors will return a Graph Query
DocumentModelMapper: Added #responsible_for? method
Edge: Added methods to receive collection classes
EdgeCollection: Handle if the definition was already added to the graph
Removed foreign key based relations
Collection: The #connection now references a vertex_collection