Fixed tooltip/popover issues

This is a fix for the tooltip/popover issues described in #609.

I also reduced the tooltip and popover initialization code down to 2 lines, instead of 3.

Examples of how to initialize tooltips and popovers:

```html
<a href="#" rel="tooltip" title="I'm a tooltip!">Link</a>
<span class="has-tooltip" title="I'm a tooltip!">Text</span>

<a href="#" rel="popover" title="I'm a popover!" data-content="Hello">Link</a>
<span class="has-popover" title="I'm a popover!" data-content="Hello">Text</span>
```