Added "geo" to SanitizationWhitelist

# Description
An Uniform Resource Identifier (URI) for geographic locations using the 'geo' scheme name. A 'geo' URI identifies a physical location in a two- or three-dimensional coordinate reference system in a compact, simple, human-readable, and protocol-independent way.[1]

The `geo` URI, like its siblings `mailto`and `tel`, works opening the link in the correct application. In this case, Android ([Maps intents](http://developer.android.com/guide/components/intents-common.html#Maps) and BlackBerry 10 (tested on my device) devices support this feature and open the link in the native map app.

# Steps to reproduce
Create a link with a geo position like: `<a href="geo:37.422,-122.084058">Google offices</a>`.

# Extra information
- [x] Test for `geo` uri
- [x] Extra ball: Test for `tel` uri
- [geo URI on Wikipedia](https://en.wikipedia.org/wiki/Geo_URI)