v1.0.0

Breaking changes:

* All environment variables now prefixed with 'THEHELP_'
* Capitalized key names now required for `Twilio.send()`, happily this allows additional paramebers to be included in the request
* `Sendgrid.send()` now requires either `text` or `html` keys be provided. Similarly, means that additional parameters can be add for inclusion in the request to Sendgrid.

Other updates:

* Comprehensive testing: unit testing and manual tests for sending/receiving messages
* All test-related environment variables now prefixed with 'TEST_'
* Removed `nodemailer`, `lodash` and `winston` as dependencies
* Add support for receiving and validating incoming Sendgrid/Twilio messages
* Pare down what's in npm package
* Updated dev dependencies