remove redundant call, add filter to GA API call, switch to date_i18n()

1) I noticed that the get_transient() call is not needed here. $results gets overwritten right after.
2) I need a filter added in to make modifications to the GA API in my own plugin. This wouldn't change any behavior, so, I hope that we can add this in. Thank you!
3) switch to date_i18n() function to account for time zone set in WP