Large dialog content or small screens causes the dialog to be positioned outside the viewport

[howlettt]

I'm submitting a ...

[ x ] bug report

Plunkr Case
http://plnkr.co/edit/sIzRqJnm5TD7ZrbpPJaH?p=preview

Current behavior
When a dialog is larger then the current screen size, the dialog is positioned outside the viewport. For example at position (-100, -100)

Expected behavior
The dialog should be positioned at the top left corner of the screen instead, position (0, 0), or at the corresponding position should the dialog only be too large in one dimension, (0, x) or (x, 0)

Minimal reproduction of the problem with instructions

• Create a dialog
  <p-dialog header="Godfather I" [(visible)]="display" modal="modal" width="350" responsive="true">
• Add a ton of text to the dialog
• Open said dialog

What is the motivation / use case for changing the behavior?
Making the dialog more responsive