Nuke all engines except for veritas
Move Engine::Veritas into {Engine, Relation::Graph::{Node, Edge}}
Remove commented code
Make the uri param required in Engine#initialize
Remove docs that no longer apply
Pass the already coerced uri down to DataObjects
Nuke pending flag from M:N self join specs < 1.9
Revert "Nuke pending flag from M:N self join specs < 1.9"

This reverts commit e321dc4670e427a64d7cc7e0b6f6ca34006a6b00.
Simplify Relationship::Iterator#each specs

This hopefully fixes the last remaining issue on
rbx-18
Don't allow rbx-18mode to fail on travis
Don't inject the engine into Relation::Graph#initialize

This was previously only used to determine the
#relation_node_class and #relation_edge_class to
use within the graph. Atm, this functionality is
not needed anymore.

I've changed Relation::Graph#initialize to support
injecting those two classes instead. However, I'm
not sure if that's really needed eventually. It's
not unlikely that this will be removed or changed
in some other not yet foreseeable way.
Inject the environment in Mapper#initialize
Keep the relation graph in the Environment instance
[WIP] Introduce DataMapper::Repository
Nuke Engine in favor of Environment#repositories
Move integration specs out of the veritas directory
Add IRC notification on successful builds
[ci skip] Update SpecHelper.draw_relation_graph
Push Mapper#environment down to Relation::Mapper
Push enumerable inclusion down to Relation::Mapper