Support for multiple handlers

Added three tests for this. This allows us to have `route.get(path,
fn1, fn2,
fnN)` but only the last handler, `fnN` will receive the next generator.
This is very useful for adding little permission checks or something
similar to your routes, they can then throw to disrupt the middleware.

Also removed soft dependency on the koa repo in favor for * from npm.
Merge pull request #11 from koajs/hallas/multiple-handlers

Support for multiple handlers