bindEmitter: handle multiple listeners correclty

Fixes #12. A clear case of, "I can't believe I ever thought that would
work." Tested with 0.10.21 and 0.8.25.
release: 2.4.4 - another bindEmitter fix
test: ensure that removeListener cleanup is working

Closes #11 by demonstrating its necessity.
bindEmitter: move EE monkeypatching into shimmer

See how much simpler this looks?
bindEmitter: use new simplified wrapEmitter API

Now the bindEmitter method actually makes sense and is only doing
CLS-related stuff. Should be slightly faster, too.
bindEmitter: emitters bound to multiple namespaces
code: allow interleaving of contexts

Popping an inner context leaves everything above it on the stack. This
is a change in behavior: previously popping a lower context also popped
contexts above them.
release: 2.5.0 - better bindEmitter (with multi-binding) and context interleaving
deps: updated async-listener
release: 2.5.1 - updated async-listener
deps: updated async-listener for better 0.8.0-3
docs: added badge
release: 2.5.2 - better 0.8 support