Add visual to Frequency Spectrum goodie

Re #300, adds visual (inline SVG) for electromagnetic and/or audible frequency ranges.
![image](https://cloud.githubusercontent.com/assets/726198/3488558/cb77b122-04ef-11e4-9899-26da233c6315.png)

@jagtalon I always have opinions! I prefer `$emMatch->{subspectrum}`.. but I don't think it makes much difference one way or the other.