Improve performance of string handling

[danielcompton]

The string.split and string/includes? calls get very expensive when there are a large number of them. We should look into a cheaper way of doing this, perhaps by creating another Reagent function which returns a vector of the component hierarchy, rather than a string.

[danielcompton]

We have a memoize over the component-path which amortises the cost, but it would probably be better to operate over data instead of splitting strings if possible.