Router.navigate executes although trigger:false with encoded hash fragment in Firefox

`Router.navigate()` will execute with `trigger:false` if the has fragment will contain url encoded characters in FireFox (tested with V39, V43).

correct behaviour in Backbone 1.1.2: https://jsfiddle.net/g9zmwmdk/10/
wrong behaviour in Backbone 1.2.3: https://jsfiddle.net/g9zmwmdk/9/

I think the new behaviour was introduced in https://github.com/jashkenas/backbone/compare/1.1.2...1.2.0#diff-0d56d0d310de7ff18b3cef9c2f8f75dcR1764

Reproduce the Firefox behavior with the linked JSFiddle examples, comparing Backbone 1.1.2 and 1.2.3. Then inspect Router.navigate and the behavior change in the linked 1.1.2-to-1.2.0 diff; done means trigger:false no longer executes navigation when the hash fragment contains URL-encoded characters.

Written by the indexing model from the issue text.