feat(RequestValidator): Adds a module that handles validating request…

[tomciopp]

…s are actually coming from Twilio

Module and tests are based off of twilio's ruby client.
https://github.com/twilio/twilio-ruby/blob/master/lib/twilio-ruby/security/request_validator.rb
https://github.com/twilio/twilio-ruby/blob/master/spec/security/request_validator_spec.rb

Here is the reference docs for this feature: https://www.twilio.com/docs/usage/security

[tomciopp]

I'm going to make a modification to the combine function. While what currently written works, it is technically incorrect. Will update with new version.

[tomciopp]

Updated with new version

[danielberkompas]

Thanks! ⭐ ⭐ ⭐