Routingpy

Added
- Valhalla `/expansion` examples in the Jupyter Notebook
- OpenTripPlanner v2 support for routing & isochrones

Fixed
- Google router's `duration` and `distance` attributes not being calculated correctly in single route response ([107](https://github.com/gis-ops/routingpy/issues/107))
- pointer issue when requesting multiple times with the same connection

Removed
- `MapboxValhalla` provider, since Mapbox doesn't expose a public Valhalla endpoint anymore

Fixed
- Graphhopper 7.0 deprecated the "vehicle" parameter for the new "profile" parammeter

Fixed
- Unit conversion did not work properly in ors' directions method
- Docstring for `intersections` parameter in ors' isochrones method was missing
- `profile` parameter was unnecessarily passed to POST params in ors' isochrones and matrix methods
- switched Graphhopper to POST endpoints & fixed any outdated parameters

Added
- Added Valhalla's trace_attributes endpoint

Fixed
- Passing a Valhalla.Waypoint to isochrones resulted in an unhandled exception

Fixed
- OSRM does have a weird URL concept for profiles, so revert [64](https://github.com/gis-ops/routing-py/issues/64))

Added
- `interval_type` to `Isochrone` and `Expansions` objects