Add more examples of costing options syntax

[rmglennon]

We have had a couple of support tickets recently (such as Desk 1295) where users have missed the syntax for costing options, usually because they are not including the model name again. The proper way is "costing_options":{"bicycle":{...}}, rather than "costing_options":{...}. Without this, they never see a difference when setting the bicycle type, for example.

We should add more examples of how to do this for all models.

{"locations":[{"lat":37.94152381803029,"lon":-121.96226477622986},{"lat":37.931335857027115,"lon":-121.97398066520691}],"costing":"bicycle","costing_options":{"bicycle":{"bicycle_type":"Mountain","use_roads":"0.5","use_hills":"0.0"}}}