Basic IR tuples; have not included CALL/RET tuples for now
Added basic IR block class; may need to come up with a name better than 'backend' for directory later
Removed ALLOC; made changes to tuple and block structures to make it easier to form graphs
Added IRGraph class; so far, only splitting up streams of IR into basic blocks (no successors indicated)
Graph building now adds successors
Merge branch 'master' of https://github.com/tcd-swift/tcd-swift into shayan
Added more declaration and type grammar