Provided popup delay for tooltip directive

[hbugdoll]

What are you changing/introducing

• Added attribute tooltip-popup-delay to tooltip directive (like in Bootstrap or AngularUI)
  • use of $timeout
  • cancel timeout on mouseleave or when tooltip is destroyed, so it don't get into conflict with other tooltips
• Example: <span tooltip tooltip-text="Tooltip" tooltip-popup-delay="500">...</span>

What is the reason for changing/introducing

• Ability to show tooltips with a delay, not only instantly

QA

Q	A
Is bugfix?	no
New feature?	yes
Breaks BC?	no
Tests pass?	yes
Fixed issues	–

[nadar]

LGTM

[hbugdoll]

Thanks for merging @nadar