Migrating from Restify 4.x to Restify 5.x. Closes #47

[mariopeixoto]

See #47.

Please review and let me know if this works for you. Since Restify 5.x removed the restify.errors property, I had to use the restify-errors package.

The most important change is that restify-errors don't allow the customization of the body, but it does allow the creation of new errors using the makeConstructor function. So the JSON output will change a little bit from { error: ..., errorDescription: ...} to { code: ..., message: ... }. Does that comply with the specification?

[itsdouges]

@domenic any word on reviewing at the PR? :)

[bialesdaniel]

Any update on whether this can be merged?