Added Zip
Small refactor of Result classes
Merge branch 'typed'

Conflicts:
	core/src/main/scala/com/rethinkscala/ast/Typed.scala
	core/src/test/scala/com/rethinkscala/ast/AstTest.scala
	core/src/test/scala/com/rethinkscala/ast/JoinTest.scala
	core/src/test/scala/com/rethinkscala/ast/SelectTest.scala
Changed produced type for IndexesOf