Tooltip detachment on transitions

• Adds automatic detachment of tooltips when their respective element is removed from the DOM
• Fixes #7

Important: This doesn't add functionality for detaching tooltips rendered using the renderChildTooltips helper. That will come in a later release because that requires additional feature work.

Functionality moved from initializer to mixin

• The core helper methods and properties for rendering tooltips are now a mixin
• Developers are not forced to have the tooltip functionality on every view

Support for Ember 1.13

0.1.1

Exclude beta from Travis required pass until ember qunit bugs are fix…