Change Webb and WebbUtils to provide a protected constructor.

Private constructor does not allow these classes to be inherited.
There are valid cases for extending the behaviour, but having a
private constructor does not allow it.
Merge pull request #6 from AppGyver/feature/allowExtending

Change Webb and WebbUtils to provide a protected constructor.

OK, I understand your point. Hopefully it helps you. Tell me, if you need a new Release version for your gradle/maven build.