Leapmotion plugin

Made sure all vars are declared with the var keyword.
	modified:   plugin/leap/leap.js

Commented out leap plugin inclusion.

modified:   plugin/leap/leap.js

Enhanced the pointer.
Cleaned up the code.
Added additional optional parameters.
Updated documentation.

modified:   README.md
modified:   index.html
modified:   plugin/leap/leap.js

Updated README.md to mention the leap plugin.
Removed leap settings from index.html.
Better variable naming in leap.js

modified:   README.md
modified:   index.html
modified:   plugin/leap/leap.js

modified:   css/reveal.min.css
modified:   plugin/leap/leap.js

Occasionally gestures were fired twice. This helps prevent that.
modified:   plugin/leap/leap.js

modified:   css/reveal.css
modified:   css/reveal.min.css
modified:   plugin/leap/leap.js

When used correctly, the 1/2 second delay is uncessary and may yield undesireable results.
modified:   plugin/leap/leap.js

Changed invert to naturalSwipe
Removed invert rule from index.html
Ensured that left/right swipes only work with 1 hand present
modified:   index.html
modified:   plugin/leap/leap.js

Added timing code to limit gesture calls.
Added gesture to access the overview.
index.html includes the leap plugin

Left, right, up, and down gestures.
Optional invert for gestures.

```html
<section data-markdown>
<script type="text/template">
</script>
</section>
```

css/theme/template/settings.scss adds the $headingMargin variable, set to `0 0 20px 0`.
css/theme/template/theme.scss uses $headingMargin to set margin on headers.