starting 0.3.0
don't accumulate test fns on each deftest evaluation
Supporting async testing, fixes gh-34:

* all test-time dynamic bindings eliminated, replaced with reified test environment(s), atoms+maps
* moved fixtures-2 namespace to properly-named file
Use dynamic binding of test context for synchronous tests, re: gh-34
add example of factored assertions to 'portable' test ns, too
Fix some misc. synchronous testing regressions, fixing gh-43:

* Call progress/completion callback immediately if the test-env indicates completion already
* Don't assume that the test-env has an :async slot
emit namespaced symbols referring to core.async macros/functions
simplifying is/try-expr interaction
add arity to test-var that accepts a test environment
whoops
only pass along uncaught exception to `done` when in an async test
Introduce new TestContext type to disambiguate contexts from environments, etc.
Throw reasonable error message when `is` is used with an explicit test context argument incorrectly, fixes gh-45
remove spurious alts! reference for ClojureScript
include cljx transformation in travis build
disable Rhino tests until it can be convinced that setTimeout is defined (!) (gh-54)