Formalize a spec runner template, allow users to override

[searls]

Right now the 'template' for the SpecRunner HTML files is stored inline in some Java. This should be pulled out to an external file or template, and perhaps loaded from the classpath in such a way that users of the plugin can override it. This way, when a limitation of the plugin prevents folks from getting a particular dependency loaded, they could resort to overriding the spec runner template.