minimize or load intro graph on demand

[jfirebaugh]

The intro graph is 1.4 MB, ~25% of iD.js, ~50% of iD.min.js, ~20% of retained memory on a fresh page load.

It should either be compressed somehow, or loaded only on demand and unloaded when finished.

[bhousel]

For now I shrunk it to 527k. It can shrink a lot more - much of the graph is river geometries that extend well beyond where the tutorial is.

var fs = require('fs'),
    _ = require('../js/lib/lodash.js');

var graph = JSON.parse(fs.readFileSync('./introGraph_orig.json', 'utf8'));
_.each(graph, function(v,k) {
    var tags = _.omit(v.tags, function(v,k) {
        if (k.indexOf('tiger:') !== -1) return true;
        if (k.indexOf('addr:') !== -1) return true;
        if (k.indexOf('gnis:') !== -1) return true;
        if (k.indexOf('is_in') !== -1) return true;
        if (['ele','source','wikipedia','website','created_by'].indexOf(k) !== -1) return true;
        return false;
    });
    graph[k] = _.omit(v, ['version','changeset','user','uid','visible','timestamp']);
    if (_.isEmpty(tags)) {
        delete graph[k].tags;
    } else {
        graph[k].tags = tags;
    }
});

fs.writeFileSync('introGraph.js', "iD.introGraph = '" + JSON.stringify(graph) + "';");

[bhousel]

For comparison, imagery.json is now at 995K

[bhousel]

Updated again, imagery.json now at 274K. We were unnecessarily pretty printing it.