Allow @...@ to match none or more elements

[Gamesh]

fixes issue #72, by allowing @...@ to match none or more elements. Also added unit tests

[norberttech]

could you also please add an example of this feature into https://github.com/coduo/php-matcher/blob/master/tests/MatcherTest.php if possible maybe in test_matcher_with_json

[Gamesh]

@norzechowicz done

[norberttech]

@Gamesh sorry it took me that long : / I added that to my todo list and forgot to merge it later