Add backtrace to rspec configuration
Change TODO note to match planned interface
Change gemspec to use a singular license
Move require statements to group similar libs together
Change code to qualify constants to avoid ambiguity in the future
Remove unnecessary namespace qualifications
Add Axiom::Tuple#to_hash
Add Axiom::Tuple#inspect
Refactor Axiom::Algebra::Join to be simpler
Add Axiom::Relation::Index
Refactor Axiom::Algebra::Join to use Axiom::Relation::Index
Add Axiom::Types::Relation type
Add Axiom::Attribute::Relation
Add Axiom::Relation::Operation::Nest
Add Axiom::Relation::Operation::Unnest