Code refactor to support SM v2 + v3

[ezimuel]

This PR contains the code refactor for support zend-servicemanager v2 and v3.

[weierophinney]

I wonder if we should finish up zend-stdlib and tag it before merging this; would make things simpler. :)

Same goes for zend-config, below.

[ezimuel]

@weierophinney I think we can tag 2.8 of zend-stdlib and 2.6 of zend-config, we have a ton of usage around with "dev-develop as".

[weierophinney]

Looks great! One other thing to consider is doing a v2/v3 compatibility test class based on the new Zend\ServiceManager\Test\CommonPluginManagerTrait, as detailed in zendframework/zend-servicemanager#93. All told, though: this looks good to go.

[ezimuel]

@weierophinney do you mean to create a test class like ZendTest\Tag\Cloud\Decorator\DecoratorPluginManagerCompatibility that acts like this class?

[weierophinney]

do you mean to create a test class like

Yes, exactly!

[weierophinney]

Since this adds the compatibility test, the v2 version references for zend-servicemanager should likely all be ^2.7.5 and the v3 references ^3.0.3. I can do that on merge, though; patch looks great!