Add --hmr-port and --hmr-hostname options to parcel watch

Fixes #575.

src/cli.js

@@ -62,6 +62,15 @@ program
     '--public-url <url>',
     'set the public URL to serve on. defaults to the same as the --out-dir option'
   )
+  .option(
+    '--hmr-port <port>',
+    'set the port to serve HMR websockets, defaults to random',
+    parseInt
+  )
+  .option(
+    '--hmr-hostname <hostname>',
+    'set the hostname of HMR websockets, defaults to location.hostname of current window'
+  )
   .option('--no-hmr', 'disable hot module replacement')
   .option('--no-cache', 'disable the filesystem cache')
   .option('--no-source-maps', 'disable sourcemaps')