Fixed to work with app-routes >= 0.1.12

chronic_between was throwing the following with a fresh install:

```
NoMethodError: undefined method `[]=' for nil:NilClass
	from ~/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/app-routes-0.1.13/lib/app-routes.rb:67:in `regex_get'
	from ~/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/app-routes-0.1.13/lib/app-routes.rb:52:in `get'
	from ~/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/chronic_between-0.2.9/lib/chronic_between.rb:55:in `ranges'
	from ~/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/chronic_between-0.2.9/lib/chronic_between.rb:23:in `within?'
	from (irb):5
	from ~/.rbenv/versions/1.9.3-p194/bin/irb:12:in `<main>'
```