Send results to auto callback when an error occurs

When an error occurs using the auto method, still send the partial
results to the callback.
Partial results should include the current task
Update README.md with auto always passing a results object
Remove setTimeout
added a cautionary note to the documentation of async.auto
Fixed typo in compose example
added default concurrency for queue, closes #249
Merge pull request #235 from leahciMic/async_auto_error_receives_partial_results

Send results to auto callback when an error occurs
Merge pull request #245 from lookfirst/master

Fixed typo in compose example.
Merge pull request #240 from brianmaissy/documentation

added a cautionary note to the documentation of async.auto