Update all methods to meet psr-4 standards

What's Changed

• Update all methods from underscores to camelCase by @carmelosantana in #2

Full Changelog: v0.2.0...v0.3.0

Full ADF specification supported

• Fixed add_phone default values
• Added complete specification from ADF 1.0
• Added new examples
• Added example-1/5.php
• Added support for full ADF implementation
• Added attribute + element
• Changed set_requestdate() to add_requestdate()
• Update composer.json
• Update docs
• Removed add()