Add as_dhall refinement
Test typechecker edge cases
Optional#value is not what we want here
Update makefile with more helpers
Run all dhal-lang typecheck tests
Run all dhall-last tests for cache_key
Run all dhall-lang tests for normalization
Pass all import tests
Allow self-describing CBOR
Environment variable failure can fallback
Allow imports to be either binary or source form
Tests are in UTF-8
Update to latest dhall-lang
Add cache_key test runner
Update to new UnionType selection semantics
Anything we'll eventually run is a skip
Fix env import decode
Fix test to new binary format

No more null fragment
Use upstreamed type tests