Unsure that returned annotation indexes are sequential
Merge pull request #72 from php-annotations/sequentinal-index-in-returned-annotation-array

Unsure that returned annotation indexes are sequential
Removing redundant code in "getUsage" method

Code, that locates parent `@usage` annotation is removed in `getUsage` method in favor code in `getAnnotations` method, that recursively obtains all annotations including ones from parent classes.