Updated required DMD version

The use of deprecated with information in parentheses didn't compile in DMD 2.059.
Merge pull request #186 from ekyo/patch-1

Updated required DMD version
Removed deprecated import.
Fixed TaskCondition.wait(), was waiting indefinitely.
Increase diagnostics for failed TaskFibers.
Extended FixedRingBuffer to be able to also work with a dynamic array as its backing.
Implemented a first version of a std.concurrency compatible API.

Still missing message box crowding handling, unlimited message boxes and handling of special exception messages.
Merge branch 'master' of github.com:rejectedsoftware/vibe.d
Added a simple application to test vibe.core.concurrency.