Support newline-delimited GeoJSON

It would be really handy if the command line tools could support [newline-delimited](http://ndjson.org/) GeoJSON, similar to Tippecanoe, [shp2json](https://github.com/mbostock/shapefile) and the ndjson-cli library.

In theory, processing newline-delimited files means memory is not a constraint, as the entire source GeoJSON doesn't need to be read into memory before processing begins. But I don't know enough about PBF to know whether that's actually true in this instance.

Start by inspecting the command line tools and how they currently process GeoJSON, then compare the newline-delimited format with Tippecanoe, shp2json, and ndjson-cli. Determine whether PBF processing can stream records without loading the entire source; done means the tools accept newline-delimited GeoJSON while preserving the expected output.

Written by the indexing model from the issue text.