Fix torrent.done state when there are deselected files (fix #316)

lib/torrent.js

@@ -1154,8 +1154,20 @@ Torrent.prototype._checkDone = function () {
     debug('file done: ' + file.name)
   })
 
-  // is the torrent done?
-  if (self.files.every(function (file) { return file.done })) {
+  // is the torrent done? (if all current selections are satisfied, or there are
+  // no selections, then torrent is done)
+  var done = true
+  for (var i = 0; i < self._selections.length; i++) {
+    var selection = self._selections[i]
+    for (var piece = selection.from; piece <= selection.to; piece++) {
+      if (!self.bitfield.get(piece)) {
+        done = false
+        break
+      }
+    }
+    if (!done) break
+  }
+  if (!self.done && done) {
     self.done = true
     self.emit('done')
     debug('torrent done: ' + self.infoHash)