Add missing import for saltURL in bin.js

[ymen]

@dasmoth

There seems to be a unresolved saltURL variable in bin.js, which seems to be solved by importing it from utils.

Discovered this when I was trying a Trix-based gene search on a Safari, which triggered an exception:

[dasmoth]

Thanks!

The following line of bin.js actually does the same thing as saltURL -- the plan way to avoid cross-module dependencies in this case -- but for some reason the call to saltURL never got removed. I've fixed this now (also 0.12.x branch).