Add `--threads=#` option for setting max threads

Make grunt NODE_ENV development by default

Gruntfile.js

@@ -8,6 +8,8 @@ var initWorker;
 var incomplete = [];
 var running = 0;
 
+env.NODE_ENV = env.NODE_ENV || 'development';
+
 module.exports = function (grunt) {
 	var args = [];
 	var initArgs = ['--build'];

src/meta/build.js

@@ -180,6 +180,11 @@ function build(targets, callback) {
 	async.series([
 		beforeBuild,
 		function (next) {
+			var threads = parseInt(nconf.get('threads'), 10);
+			if (threads) {
+				require('./minifier').maxThreads = threads - 1;
+			}
+
 			var parallel = !nconf.get('series');
 			if (parallel) {
 				winston.info('[build] Building in parallel mode');

src/meta/minifier.js

@@ -41,9 +41,21 @@ function setupDebugging() {
 var pool = [];
 var free = [];
 
-Minifier.maxThreads = os.cpus().length - 1;
+var maxThreads = 0;
+
+Object.defineProperty(Minifier, 'maxThreads', {
+	get: function () {
+		return maxThreads;
+	},
+	set: function (val) {
+		maxThreads = val;
+		winston.verbose('[minifier] utilizing a maximum of ' + maxThreads + ' additional threads');
+	},
+	configurable: true,
+	enumerable: true,
+});
 
-winston.verbose('[minifier] utilizing a maximum of ' + Minifier.maxThreads + ' additional threads');
+Minifier.maxThreads = os.cpus().length - 1;
 
 Minifier.killAll = function () {
 	pool.forEach(function (child) {