Input forwarding of multiple parameters in a ComposedOperation

Adds tests for passing multiple parameters from operation to operation in an operation pipeline.
Improves flexibility of Operation#fail

The method now supports the same interface as Ruby's own raise. The only difference is that the method raises an exception of the type that is specified by Operation.exception if no exception is supplied as an argument.

Furthermore, Operation#fail now forces the operation's result to be nil.
Merges Feature: Custom Exceptions
Updates version: v0.7.0 -> v0.8.0
Release v0.8.0