add unhandled exception handler for cusomization of PromisePipe default behavior

[edjafarov]

Right now on unhandled exception it just fails like this:

Failed inside test
ReferenceError: ff is not defined
Object.test@/Users/edjafarov/work/PromisePipe/tests/PromisePipe.error.spec.js:28:16
newArgFunc@/Users/edjafarov/work/PromisePipe/src/PromisePipe.js:456:26
{anonymous}() ($)$$internal$$tryCatch@/Users/edjafarov/work/PromisePipe/node_modules/es6-promise/dist/es6-promise.js:304:16
{anonymous}() ($)$$internal$$invokeCallback@/Users/edjafarov/work/PromisePipe/node_modules/es6-promise/dist/es6-promise.js:316:17
{anonymous}()@/Users/edjafarov/work/PromisePipe/node_modules/es6-promise/dist/es6-promise.js:874:13
{anonymous}() ($)$asap$$flush@/Users/edjafarov/work/PromisePipe/node_modules/es6-promise/dist/es6-promise.js:111:9
process._tickCallback@node.js:442:13

and it fails like this in the chain
we need to catch it at the end of chain and allow to assign default handler

[jukkasi]

+1