adding basic tests for default failures in composite
introducing propagateFailure flag for childs in composite addon to denotate when a child failure should make the parent to fail as well.
Merge branch 'develop' of github.com:yahoo/mojito into composite-errors
refactor to simplify the code and allow others to leverage ac.composite to do other parallel dispatching routines
Merge branch 'develop' of github.com:yahoo/mojito into composite-errors
implementing feedback from review.
Merge pull request #978 from caridy/composite-errors

Fixes issue #865. Fixes issue #25: `mojito-composite-addon` error propagation by flagging a child with `propagateFailure` flag.