Add the `param` helper
Add the `param` helper

Since we already have the `queryParam` helper, it only makes sense to also have the `param` helper, especially since Meteor 1.2 will bring in nested helpers.
mquandalle/meteor-flow-router-helpers,arillo/meteor-flow-router-helpers,arillo/meteor-flow-router-helpers,sungwoncho/meteor-flow-router-helpers,adrprado/meteor-flow-router-helpers,serkandurusoy/meteor-flow-router-helpers