Amend documentation to prefer match_array over =~

During a discussion on IRC about matching arrays @alindeman suggested the use of match_array but the Relish docs made almost no mention of it so he suggested that as it is actually the preferred syntax we should alter the features to refer to it over the =~ operator.

I also amended the README files to show examples of use so that others realise this matcher exists. I wasn't totally sure but I felt that using 'array' over 'actual' in the README and features conveyed the expectation of comparing arrays - though the matcher name should be a big clue :smile: