Code Samples / Resources for Polyline Encoding

[dnesbitt61]

Add some code samples to encode/decode Valhalla polylines (6 degree precision).
Link to these code samples in the API docs

[kevinkreiser]

we have plenty of decoding examples and a demo:

http://valhalla.github.io/demos/polyline/
https://github.com/valhalla/valhalla-docs/blob/master/decoding.md

encoding shoudn't be too much work to port around. i'm pretty sure we have it in c++ and javascript