1.18.20160930145650: Optimize validate (#60)

Validation can now either fail fast (raise_ex=False) or fail with
explanation (raise_ex=True).  Improve validation performance by using fail fast
when checking unions.  Optimize record validation by performing explicit check
for "class" first.  Improve validation error reporting for unions when one of
the types is an exact match for class by suppressing errors for other types in
the union.

Other changes:
* Use unicode strings more consistently.
* makedoc applies table styling
* Add version constraint to lockfile package dependency