deploy: add `--public` option

To create a deployment as "public" (`/_src` route works)
when the user has a "premium" plan.

bin/now-deploy

@@ -25,6 +25,7 @@ const argv = minimist(process.argv.slice(2), {
     force: 'f',
     forceSync: 'F',
     login: 'L',
+    public: 'p',
     'no-clipboard': 'C',
     'forward-npm': 'N'
   }
@@ -50,6 +51,7 @@ const help = () => {
     -d, --debug         debug mode [off]
     -f, --force         force a new deployment even if nothing has changed
     -L, --login         configure login
+    -p, --public        deployment is public (\`/_src\` is exposed) [on for oss, off for premium]
     -C, --no-clipboard  do not attempt to copy URL to clipboard
     -N, --forward-npm   Forward login information to install private NPM modules
 
@@ -102,6 +104,7 @@ const forwardNpm = argv['forward-npm'];
 const forceNew = argv.force;
 const forceSync = argv.forceSync;
 const shouldLogin = argv.login;
+const wantsPublic = argv.public;
 const apiUrl = argv.url || 'https://api.zeit.co';
 const isTTY = process.stdout.isTTY;
 const quiet = !isTTY;
@@ -227,7 +230,8 @@ async function sync (token) {
       forceNew,
       forceSync,
       forwardNpm: alwaysForwardNpm || forwardNpm,
-      quiet
+      quiet,
+      public: wantsPublic
     });
   } catch (err) {
     if (debug) console.log(`> [debug] error: ${err.stack}`);