Map types are generic
Useful helper for the common typecheck cases
Allow arbitrary ruby objects to live in the AST

Only for when you're really sure you want that.
Method#as_dhall just like Proc#as_dhall
Prelude Map becomes Hash
Add Map type from Prelude
Allow unannotated format string tokens
Update to latest dhall-lang
Fix expectations for tests
Refactor projection typecheck
Multihash prefix on filename
This could be a literal, so may be frozen
New header format
Support \u{XXX} and ban surrogates
implement as Location and use URI internally
Tests can be long and procedure like
Record projection by expression / type
Do not commute multiplication when normalizing