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.
Merge pull request #70 from php-annotations/remove-redundant-usage-annotation-handling

Removing redundant code in "getUsage" method
Adding more tests to increase coverage

- solving problems with too long lines
- code usage in test constructor wasn't reflected in coverage report
- expected exception wasn't reset after each test
- simplify exception catching in existing tests
- test suite wasn't assessing that expected exception wasn't thrown at all