Update scripts and docs to use yarn where appropriate

Most `npm` operations are replaced with `yarn`, which generally has better
behavior. However, steps like publish that write to the NPM registry are left to
`npm`, which currently handles these tasks best.

scripts/yarn-sub.js

@@ -0,0 +1,22 @@
+const path = require('path');
+const child_process = require('child_process');
+
+const moduleName = process.argv[2];
+if (!moduleName) {
+    console.error("Expected module name");
+    process.exit(1);
+}
+
+const argString = process.argv.length > 3 ? process.argv.slice(3).join(" ") : "";
+if (!argString) {
+    console.error("Expected an yarn argument string to use");
+    process.exit(1);
+}
+
+const modulePath = path.dirname(require.resolve(`${moduleName}/package.json`));
+
+child_process.execSync("yarn " + argString, {
+    env: process.env,
+    cwd: modulePath,
+    stdio: ['inherit', 'inherit', 'inherit'],
+});