Locking down js-routes version

Locking down js-routes to 0.6.x as 0.7.5 generates this:

```javascript
organizations_path: function(options) {
  return Utils.build_path(0, ["/organizations"], arguments)
},
```

Whereas js-routes 0.6.2 generates this:

```javascript
organizations_path: function(options) {
  return Utils.build_path(1, ["/organizations"], arguments)
},
```

Our javascript relies on the 0.6.2 route.