Eject Windows drives after successful burning

Use the `removedrive` for this task:

https://github.com/jviotti/removedrive

Fixes: https://github.com/resin-io/herostratus/issues/40

lib/src/writer.js

@@ -25,6 +25,12 @@ var imageWrite = require('resin-image-write');
 var Promise = require('bluebird');
 var umount = Promise.promisifyAll(require('umount'));
 var fs = require('fs');
+var os = require('os');
+var isWindows = os.platform() === 'win32';
+
+if (isWindows) {
+  var removedrive = Promise.promisifyAll(require('removedrive'));
+}
 
 /**
  * @summary Get image readable stream
@@ -86,6 +92,10 @@ exports.writeImage = function(image, drive, onProgress) {
       writer.on('done', resolve);
     });
   }).then(function() {
-    return umount.umountAsync(drive.device);
+    if (isWindows && drive.mountpoint) {
+      return removedrive.ejectAsync(drive.mountpoint);
+    } else {
+      return umount.umountAsync(drive.device);
+    }
   });
 };

package.json

@@ -16,6 +16,9 @@
   },
   "author": "Juan Cruz Viotti <juan@resin.io>",
   "license": "MIT",
+  "optionalDependencies": {
+    "removedrive": "^1.0.0"
+  },
   "dependencies": {
     "angular": "^1.4.6",
     "angular-ui-bootstrap": "^0.14.2",