Bump version to 1.17.0.
Bump version to 1.17.0.

It appears as if 1.16.x was skipped, but this is not the case; 1.16.0
and 1.16.1 were tagged and published to Packagist, but this was not
represented in the code

messagebird/php-rest-api,dennisvdvliet/php-rest-api