anchor.diff:  waiting on futures to complete whose results will be discarded.
   
   Additionally, while the scala parallel collections correctly handle multiple
  -concurrent exceptions, +Future.sequence+ only returns the first exception
  +parallel exceptions, +Future.sequence+ only returns the first exception
   encountered. In +Future.sequence+, all further exceptions past the first are
   discarded. The +merge+ and +flatMerge+ methods fix these problems by throwing
   +ConcurrentThrowable+. +ConcurrentThrowable+ has a member method to access both
  
positive.code: 
  In the example below, all futures are started at the same time by
  +async.par.run+ which returns a +Future[(Int,Int,Int)]+ that completes once all
  supplied futures complete. After this returned Future completes, the tuple value
  results can be extracted using normal Scala idioms.
  
  .Example 7: +async.par.run+ workflow
  
negative.code: number of workers is limited to two, progress is reported once a second and
  certain failures are retried.
  
  .Example 8: +async.par.run+ workflow with two workers, progress reporting and failure retry
  [source,scala,numbered]
  ----
  for {
  