demonstrate asynchronous execution (-j (jobs) limits not supported)
limit number of jobs using semaphores
commit examples of workflow and its output in png
integrate asynchronous execution in core.clj
refactoring
remove binary files
add -j as non-flag-short
set-jobs-semaphore got mistakenly lost in merge
error handling
Disable stdin redirection when async is on (jobs > 1) #53
Better error messages #53
Tried tightening up async #53
For #53 got all test working, but a bit of a hack
Fix all but one test for async
Fixes for determistic run and to get tests working #53

There was a test where a workflow had a cycle, but if you specified a
down-tree target, there was no cycle.  This test was failing, now it
works.
Merge branch 'develop' into feature/async-53

Conflicts:
	src/drake/core.clj
	test/drake/test/utils.clj
Code review fixes #53 and some cleanup

Simplify assoc-deps
Remove original run-steps
Simplify expand-step-recur
Fix regression tests
Finished code review items for #53
Fixed small error in refactoring #53
Made code review changes for #91 #53

Moved import statement into ns
Removed defunct comments
Better comments on run-steps-async
Refactored adding empty promises to steps