use trap function
more trapping
RED: failing test for conc() functionality
RED: Trying to impl. conc() to answer just the simple case of a single
function has failed.  This can be thought of as fake-it.

  $ time jasmine-node --captureExceptions spec
  ............................F.....Promoting slug a_slug_id to prod.
  >>>>>>>>>> ALL'S WELL
  "Deploying a_slug_id to app b {Promotion of: most_recent_at_a}"
  ....Promoting slug a_slug_id to prod.
  .............

  Failures:

    1) FunFlow conc can execute a single function
     Message:
       timeout: timed out after 5000 msec waiting for spec to complete
     Stacktrace:
       undefined

  Finished in 6.857 seconds
  51 tests, 103 assertions, 1 failure, 0 skipped

  real	0m7.959s
  user	0m2.200s
  sys	0m0.160s

  shell returned 1
Revert "RED: Trying to impl. conc() to answer just the simple case of a single"

This reverts commit 55220391c061a90c3f30c8e62e21ef4e116a98fb.
GREEN: fake it
GREEN: generalize to any single value
GREEN: new test introduced & implemented - passing a failure from a single function
GREEN: new test introduced & implemented - a function invoked by conc() can emit several values
RED: failing test for conc() with two functions
GREEN: impl. it for two functions
REFACTOR (slightly)
REFACTOR: generalize to n functions
REFACTOR: stop sepcial casing the single-function scenario
REFACTOR: rename f1 (leftover from specialization) to f
sanity: many functions, many values
GREEN (false positive): Introduce a bug into the code, not caught by the tests
RED: A-ha. Here's a test that captured the bug.

    Failures:

      1) FunFlow conc emits results using the ordering of the functions that were passed to it
       Message:
         Expected [ 'FROM SECOND FUNCTION' ] to equal [ 'FROM FIRST FUNCTION' ].
       Stacktrace:
         Error: Expected [ 'FROM SECOND FUNCTION' ] to equal [ 'FROM FIRST FUNCTION' ].
        at trap (/home/imaman/workspace/green-site/spec/funflow.spec.js:172:22)
        at applyAt (/home/imaman/workspace/green-site/funflow.js:43:16)
        at next (/home/imaman/workspace/green-site/funflow.js:55:22)
        at /home/imaman/workspace/green-site/funflow.js:30:31
        at /home/imaman/workspace/green-site/spec/funflow.spec.js:177:56
        at process._tickCallback (node.js:415:13)

      2) FunFlow conc emits results using the ordering of the functions that were passed to it
       Message:
         Expected [ 'FROM FIRST FUNCTION' ] to equal [ 'FROM SECOND FUNCTION' ].
       Stacktrace:
         Error: Expected [ 'FROM FIRST FUNCTION' ] to equal [ 'FROM SECOND FUNCTION' ].
        at trap (/home/imaman/workspace/green-site/spec/funflow.spec.js:173:22)
        at applyAt (/home/imaman/workspace/green-site/funflow.js:43:16)
        at next (/home/imaman/workspace/green-site/funflow.js:55:22)
        at /home/imaman/workspace/green-site/funflow.js:30:31
        at /home/imaman/workspace/green-site/spec/funflow.spec.js:177:56
        at process._tickCallback (node.js:415:13)

    Finished in 1.637 seconds
    56 tests, 112 assertions, 2 failures, 0 skipped
GREEN: un-introduce the bug. Test passes
RED: try to use the newly introduced FunFlow.conc() method in prod. code