adding Lazy Variables
checking lazy vars lazily
minor
examples
update README
more examples
minor
motivation
starting mutual recursion
establish termination
fix for #116
test editing
remove lazy var from environment, when checking its definition -- if not we can have infinite loop
from list to hashmap
only check lazyvars in the root module, and revert some changes
Merge pull request #117 from ucsd-progsys/lazyVars

Lazy vars