use opn for cross-os compatibility. fixes #21

package.json

@@ -27,6 +27,7 @@
     "micro-css": "^0.5.0",
     "observ": "^0.2.0",
     "observ-struct": "^6.0.0",
+    "opn": "^5.1.0",
     "stereo-panner-node": "~0.2.0",
     "through2": "^0.6.5"
   },

run.js

@@ -1,13 +1,14 @@
 #!/usr/bin/env node
 var exec = require('child_process').exec
+var opn = require('opn');
 
 process.chdir(__dirname)
 var runner = exec('npm start')
 
 console.log('Starting server...')
 setTimeout(function () {
   console.log('Go to http://localhost:9966')
-  exec('open http://localhost:9966')
+  opn('http://localhost:9966')
   runner.stdout.pipe(process.stdout)
   runner.stderr.pipe(process.stderr)
 }, 2000)