Added Attean::API::TriplePattern and Attean::API::QuadPattern roles.
Added Attean::TriplePattern and Attean::QuadPattern classes.
Added Attean::API::TripleOrQuadPattern role.
Added Attean::API::ResultIterator role.
Removed unused code in t/expression.t.
Added Attean::Result->as_string method.
Added Attean::SimpleQueryEvaluator.