cast returned filesize to int as hinted in admin form fields renderer

[holystix]

Without the (int) cast the following error is triggered, when attempting to open a controller where ArboryImage field is used:
Type error: Return value of Arbory\Base\Admin\Form\Fields\Renderer\FileSize::getSizeInBytes() must be of the type integer, string returned

[coveralls]

Coverage remained the same at 2.219% when pulling ad10c00 on holystix:development into 671998f on arbory:master.

[coveralls]

Coverage remained the same at 2.216% when pulling 244d35c on holystix:development into 5180709 on arbory:master.

[coveralls]

Coverage remained the same at 2.216% when pulling 244d35c on holystix:development into 5180709 on arbory:master.

[coveralls]

Coverage decreased (-0.003%) to 2.214% when pulling 099e109 on holystix:development into 35c70b3 on arbory:master.

[coveralls]

Coverage decreased (-0.003%) to 2.214% when pulling 099e109 on holystix:development into 35c70b3 on arbory:master.