Extract Open Street Map (OSM) shapefiles for census tracts

[mwesterfield]

It is too expensive to use Google Street View to calculate the Green View Index for all of San Diego. We could, however, run the Treepedia scripts on individual census tracts and then stitch the results together later. We need a method to extract OSM shapefiles for each census tract in the City of San Diego. [Census tracts are the preferred subdivision for this project because other City metrics (such as the Climate Equity Index) are calculated per tract.]