use data_error and schema_error definitions

use OTP_RELEASE macro (OTP 21+). ref for-GET#70

Use OTP 21

update changelog

Merge pull request for-GET#49 from JakubCzarniecki/fix-missing-deps-f…

…or-rebar3

Add missing rfc3339 application

use rfc3339 with R15 compatibility

updated AUTHORS CHANGELOG.md

Update AUTHORS file

fix mode detection for elvis.config

Bump version