When enabled, any middleware dispatch is no longer wrapped in try/catch
blocks, allowing for exceptions/throwables to bubble out.

Added `$raiseThrowables` property and `raiseThrowables()` method, with
the former defaulting to `false` for backwards compatibility.

Has the following behavior:

- Enables the same flag in the `Dispatch` instance composed.
- If enabled and `$err` is passed to `__invoke()`:
  - Throwable/Exception values are simply thrown.
  - String arguments are used as the message for a new `MiddlewareException`.
  - Scalar values are reported in a new `MiddlewareException`
  - Array value *types* are reported in a new `MiddlewareException`
  - Object *types* are reported in a new `MiddlewareException`
  - Non-throwable/exception types trigger the deprecation notice

- Disabled by default
- `raiseThrowables()` enables it
- When enabled, calls same method on `Next` instance after creating it

…ndling-v2

Forward-ports zendframework#78 to dev-2.0.0.

Conflicts:
	src/Dispatch.php
	src/MiddlewarePipe.php
	src/Next.php
	test/DispatchTest.php
	test/NextTest.php

Removed section on $out, and replaced with detail on $delegate.

Ensure all paths in Dispatch are covered.

…ndling-v2

Forward port changes made for zendframework#78 (in this case, tests that are no
longer applicable).

Conflicts:
	test/DispatchTest.php

…ndling-v2

Forward port changes from zendframework#78.

Conflicts:
	src/Dispatch.php