Added lots :
Attribute#equal
Attribute#coerce -> rewrote
Header#constructor -> rewrote
Moved header coercion procedure that was in Relation#constructor to Header#coerce
Moved tuple coercion procedure that was in Relation#constructor to Tuple#coerce
Added some better coercion methods in helpers/coerce
Added Compose operator
Corrected the tests to play good with all this
Generated Docs, though did not go through them for changes. The API is basically the same anyways.