Make sure the Redex pattern language's 'boolean' is rendered as a nonterminal
Redex: fix a small bug in the list-machine example
Avoid doing the 2nd pass twice at the top-level

Thanks to Eric for pointing this out.
Add examples for `for/lists`
Fix regression for (begin) and simplify
Fixed in-generator's handling of arity zero.

Also combined expansion of in-generator for both expression and sequence
contexts, and made a number of places that were handling arity dynamically
to handle it statically instead.
Fixed collects/meta/props so that `props verify' runs without error.
fix docs for redex-generator
Reduce code duplication in Redex enum
Added var-except
Minor change to Redex contracts to maintain bijection internally
Simplified redex enumeration internals