Release 0.3.0

Consistency changes, stricter code usage enforcing and refactoring to split responsibilities.

Added

• On the dev side of things we now include PHP Insights to get some valuable insights about the code.

Changed

• Although discouraged by some people, we like the Exception suffix for custom exception classes. A missing `Exception` suffix in the class name for class `NorseBlue\ExtensibleObjects\Exceptions\ClassNotExtensionMethod` was added to be consistent with the naming conventions.
• We really like type hints were they are helpful, so we added a `declare(strict_types=1);` on all of our files. This could potentially be a BC change, so please test your code thoroughly.
• We declared some classes and methods as final now, as they are not supposed to be modified or extended. Some of the reasoning behind these changes is fantastically explained by Brent in his blog post titled SOLID, interfaces and final - Rant With Brent 01. If you were relying on extending or overloading these methods or classes your code could break. (Commit #8ee6a5)
• The core trait has been given some love. We split the responsibility of verifying and loading an extension method to its own class `NorseBlue\ExtensibleObjects\ExtensionMethodLoader`, now the `NorseBlue\ExtensionObjects\Tratis\HandlesExtensionMethods` is much leaner.

Fixed

• With the changes made in a recent release to also include the parent extension methods in child classes, we forgot to also update the contract (which could potentially break havoc, though minimized if using the included trait, if the needed methods were not available in your class). We are sometimes forgetful, but now it is corrected: the `NorseBlue\ExtensibleObjects\Contracts\Extensible` now has the proper methods declared. (Commit #4eae29)

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