payload validation processing updated dwyl#299 thanks to @icetbr

Add support for Hapi v18 see: dwyl#295

@dominykas add support for verifying long running request tokens see: d…

…wyl#287

Readd promise support to response function see: dwyl#271 & dwyl#272 t…

…hanks to @ethanrubio ✨

update linting to use eslint & "prettier". only "cosmetic" changes ma…

…de to module. see: dwyl#268

Major Update to Hapi v.17 (Breaking Changes to use "async function") …

…see: hapijs/hapi#3658 (release notes) ref: dwyl#248 thanks to @salzhrani for dwyl#249 🎉

moved payload: options.payload to end of index.js and reduced duplica…

…tion in tests for clarity

Final Dependency Update for Hapi v.16-compatible Apps. No Code change…

…d. See: dwyl#255 preparing for Hapi v.17

maintenance update: version of dependencies to latest. no code changed. 

dwyl#242

update devDependency on Hapi to v16. confirms that no update to code …

…is required. dwyl#215