It's impossible to install the package by adding "globalcitizen/php-iban": "3.0.0" to the composer.json as it described in the README.md.

Here is the error I got from composer:
The requested package globalcitizen/php-iban ^3.0 exists as globalcitizen/php-iban[dev-master, v1.4.9, v1.5.0, v1.6.0, v2.0.0, v2.0.1, v2.1.0, v2.1.1, v2.1.2, v2.1.3, v2.1.4, v2.1.5, v2.1.6, v2.1.7, v2.1.8, v2.1.9, v2.2.0, v2.3.0, v2.3.1, v2.4.0, v2.4.1, v2.4.10, v2.4.11, v2.4.13, v2.4.14, v2.4.15, v2.4.16, v2.4.17, v2.4.18, v2.4.19, v2.4.2, v2.4.20, v2.4.3, v2.4.4, v2.4.5, v2.4.6, v2.4.7, v2.4.8, v2.4.9, v2.5.0, v2.5.1, v2.5.2, v2.5.3, v2.5.4, v2.5.5, v2.5.6, v2.5.7, v2.5.8, v2.5.9, v2.6.0, v2.6.1, v2.6.2, v2.6.3, v2.6.4, v2.6.5, v2.6.6, v2.6.7, v2.6.8, v2.6.9, v2.7.0, v2.7.1, v2.7.2, v2.7.3, v2.7.4, v2.7.5, v2.8.0] but these are rejected by your constraint.