The 'try' impl for 'Outcome' allows the '?' operator to be used with
'Outcome' values. This is likely to make 'FromRequest' and 'FromData'
implementations more ergonomic.
This commit also expands the 'IntoOutcome' trait. It is now
implemented for 'Option'. It also now includes an additional
'or_forward' method.
This is a breaking change to `IntoOutcome`.
The MsgPack and JSON types now use `into_outcome` to generate the final
`Outcome` from their `FromData` implementations.
Resolves#98.
Summary of changes:
* Request no longer has a lifetime parameter.
* Handler type now includes a `Data` parameter.
* Response is now an enum that is either `Complete` or `Forward`.
* Outcome enum is now one of: Success, Failure, Forward.
* Outcome::Foward for Responses must include StatusCode.
* Responders are now final: they cannot forward to requests. (!!)
* Responsers may only forward to catchers. (!!)
* Response no longer provides wrapping methods.
* Route is now cloneable.
This change is fundamental to enabling streaming requests.