feat(tooltip): add multiple trigger support

[wesleycho]

• Adds support for multiple triggers

Plunker in action here.

This implements #3987.

[Foxandxss]

I don't understand this plunker. Empty input and then the tooltip.

[wesleycho]

The Plunker is a bit confusing - in the original plunker in the issue referenced, click the second item, then use shift + tab and tab to navigate back and forth. The tooltip will remain due to lack of support for multiple triggers - this feature implements support for multiple triggers (repeating the behavior will behave as expected in my Plunker).

[Foxandxss]

I see it now, LGTM.