+ Kernel#describe extended to splat additional_desc.
+ Spec#spec_type extended to take a splat of additional items, passed to matcher procs.

This should close #442 and #341.
[git-p4: depot-paths = "//src/minitest/dev/": change = 9550]
- minitest/spec should require minitest/test, not minitest/unit. (doudou)
[git-p4: depot-paths = "//src/minitest/dev/": change = 9556]
prepped for release
[git-p4: depot-paths = "//src/minitest/dev/": change = 9561]
Refactored duplication out of my tests. yay metametameta!

[git-p4: depot-paths = "//src/minitest/dev/": change = 9574]
Added minitest-stately to readme
[git-p4: depot-paths = "//src/minitest/dev/": change = 9667]
Added minitest-bang to readme
[git-p4: depot-paths = "//src/minitest/dev/": change = 9668]