Compatibility with ServiceManager v3

[mtymek]

This PR makes updates necessary for this component to work under both Service Manager v2 and v3.

Changes:

• Extracted factories for UrlHelper and ServerUrlHelper into separate classes.
• Updated required service manager version to ^2.7.5 || ^3.0.3.

• Updated extracted factories to detect SMv2 and pull dependencies from main service locator:

  if (! method_exists($container, 'configure') && method_exists($container, 'getServiceLocator')) {
  $container = $container->getServiceLocator();
  }

• Updated ZendViewRendererFactory to inject view helpers in a way that is compatible with both SMv2 and SMv3.
• Updated Travis test matrix to test with both SMv2 and SMv3

[vaclavvanik]

could be merged?

[mtymek]

@weierophinney could you please look into merging this? thanks!

[mtymek]

Looks like SMv3 compatibility was already added in #22. Closing.