This commit protects ReactiveCommand and ReactiveAsyncCommand from exceptions thrown inside a Subscribe, and marshals them to ThrownExceptions. Normally Rx doesn't guard against this kind of operation and regards it as undefined behavior, but in the ReactiveUI case, users are often doing non-trivial operations in the Subscribe, so make their life a little saner.
…cause of Rx's brokenness on WP8
…endencyObject. Fixes #120