add_fallback to provide a matcher/handler that always comes last
improve test to only work with add_callback

for some reason, adding the generic regex last makes it come first in
matchers. Now, if you change add_fallback to map, it would fail.
cleanup test and clear matchers and fallback to avoid crossover
Version 1.6.0
added Sam Beam to the Contributers list
handle nil attribute values (nil != missing)