fix(a): make anchors in SVGs work

Previously, anchors in SVGs with any prefix namespace for the href
attribute wouldn't work because jqLite uses getAttribute to retrieve
the href attribute and is unaware of namespaces.

Add a check for the xlink namespaced `href` in case it exists.

Right now the tests are just checking IE version for SVG support. However, it probably should use SVG feature detection. Or alternatively, tests shouldn't even use the `svg` element and just apply the namespaces without regard to SVG support.

Example of this (remove `ng-app` and the example will work):
http://jsfiddle.net/sirhc/2WLZx/