Convert type rules to return expression_ref and not string.
Add rule for gtycon -- as a string.
Merge branch 'master' of github.com:bredelings/BAli-Phy
Parse atype, btype, and type.
Add rules to parse constructor expressions.
Parse type, data, and newtype declarations.
Fix the definition of constrs.
Fix constr rule.
Allow defining constructors in Haskell files.
Improve comment.
Move definition of Maybe to Prelude.hs.
Move definition of IO a to Prelude.hs.
Move Range constructors to Range.hs.
Add constructors to Distributions.hs.
Move definition of Tree to Tree.hs.