Validate enum creation rules and fix bug

• Throw an exception on non-final enum classes or pubic constructor (#21)
• Fix abstract classes initialization (#18)

v0.3.0

Disallow serialization with Serialization Interface.

v0.2.0

Release contains only BC safe changes. Now, the library includes lightweight static constructor initialiser that is based on decorator for Composer autoloader.

v0.1.0

It is the first release. All future announcements will follow semantic versioning. Currently, we release 0.1.0 just because we assume that might appear issues during library adoption in new projects that will require BC breaks.
Anyway, the library API is pretty stable, so we hope to release the first major release as soon as possible.