Fix TLS issue with OTP 23

This minor update bumps Hackney to 1.17.0 to resolve the TLS hostname mismatch issue with OTP 23.

Minor update

• Verified all tests pass and noted project is still feature complete.
• Update non-production deps.

Elixir 1.7+ and updating deps

In this exciting update...

• Minimum elixir version is now 1.7
• Some deps are updated.
• All tests passed and no new magic values were found in the twilio docs.
• Skipped version 1.0.4 -- Whoops.

Update deps

Updating deps for the new ex_doc

Bump deps

• Bump depdencies
• No breaking changes
• No new functionality
• All tests still pass

Version 1.0.0 published to hex and hexdocs

No new issues have cropped up. Code is up to date with Twilio docs. I now consider this production ready, even though it's just for testing.