Fix #499, #500
Fold constants (fix #504)
Fixing crash when a library's dependency could not be loaded.

Signed-off-by: Nicolas Williams <nico@cryptonector.com>
Add `first`, `nth`, `last` (fix #510)
Add capture; document regular expression filters

    Fix #493.
Add @wtlangford to the AUTHORS list
Correct @wtlangford's address
Some builtins are unnecessarily special (fix #521)