Updated to use seneca@0.5.17, tests passing.

Ref #5.

* Updated instances of deprecated `seneca.fail(…, callback)`

Updated tests:
* seneca throws on non-mapped action pattern as of rjrodger/seneca@237b343d8985d88a8e27fc8b1ff3a2dee9d67d36 (`instance.fail` was called prior to this)
* err.valmap added in rjrodger/seneca@cd8024f40444c0d6b6396d351d34f5d2439c5c1b