Links for tuple routes are incorrect

[morganney]

For example, this route http://restbus.info/api/agencies/sf-muni/tuples/F:5650,N:6997/predictions produces the following links:

The from is really the self and reconsider the semantics of from and whether for this resource it should be a list of stop predictions used in the tuple:

[
  /agencies/sf-muni/routes/F/stops/5650/predictions
  /agencies/sf-muni/routes/N/stops/6997/predictions
]