Add build script

So it can be used for initial deploys or manual builds.
Otherwise it only builds via the incoming webhook.

build.js

+'use strict';
+const metalsmith = require('./metalsmith.js');
+const loggers = require('./lib/logging.js').loggers;
+
+const buildlog = loggers.build;
+
+buildlog.info('starting build...')
+metalsmith().build(function(err) {
+    if (err)
+        buildlog.error('build exception', err);
+})
+buildlog.info('completed build.')
\ No newline at end of file