Remove short array syntax for compatability with PHP < 5.4

As I commented in #84, if you are running PHP CLI < 5.4, you will receive an "unexpected '['" error. Reverted back to array('key' => 'value') from the short array syntax ['key' => 'value']. Should now be 5.3 compatible. Note: I also initiated a pull request for JeffreyWay/Laravel-Test-Helpers repo to fix the same issue. Thanks!