How to show the data returned via hook_views_data() in a page?
You should be able to print the output to the page using print_r. Just add print_r($data) at the end of the function, before your return statement. 

If you're just printing this data out so you can take a look at it for debugging purposes than you might want to use error_log instead. For error_log just add error_log(print_r($data, 1)) at the end of your function, before the return statement.