use new upload URL
fix an autobug

java.lang.NullPointerException
at android.hardware.usb.UsbRequest.dequeue(UsbRequest.java:155)
at android.hardware.usb.UsbDeviceConnection.requestWait(UsbDeviceConnection.java:156)
at com.geeksville.aserial.AsyncSerial.readBuffer(AsyncSerial.scala:124)
at com.geeksville.andropilot.service.USBAndroidSerial$$anon$2.fillBuffer(AndroidSerial.scala:70)
at com.geeksville.andropilot.service.USBAndroidSerial$$anon$2.read(AndroidSerial.scala:109)
at java.io.InputStream.read(InputStream.java:163)
at com.geeksville.andropilot.service.USBAndroidSerial$$anon$2.read(AndroidSerial.scala:53)
at java.io.DataInputStream.readByte(DataInputStream.java:96)
at org.mavlink.MAVLinkReader.readNextMessage(MAVLinkReader.java:179)
at org.mavlink.MAVLinkReader.getNextMessage(MAVLinkReader.java:130)
at com.geeksville.mavlink.MavlinkStream$$anonfun$com$geeksville$mavlink$MavlinkStream$$rxWorker$2.apply(MavlinkStream.scala:88)
at com.geeksville.mavlink.MavlinkStream$$anonfun$com$geeksville$mavlink$MavlinkStream$$rxWorker$2.apply(MavlinkStream.scala:72)
at com.geeksville.util.Using$.using(Using.scala:20)
at com.geeksville.mavlink.MavlinkStream.com$geeksville$mavlink$MavlinkStream$$rxWorker(MavlinkStream.scala:72)
at com.geeksville.mavlink.MavlinkStream$$anonfun$1.apply(MavlinkStream.scala:37)
at com.geeksville.mavlink.MavlinkStream$$anonfun$1.apply(MavlinkStream.scala:37)
at com.geeksville.util.ThreadTools$$anon$1.run(ThreadTools.scala:11)
at java.lang.Thread.run(Thread.java:856)
fix an autobug:

java.lang.NullPointerException
at scala.collection.mutable.ArrayOps$ofRef$.length$extension(ArrayOps.scala:111)
at scala.collection.mutable.ArrayOps$ofRef.length(ArrayOps.scala:111)
at scala.collection.IndexedSeqOptimized$class.isEmpty(IndexedSeqOptimized.scala:27)
at scala.collection.mutable.ArrayOps$ofRef.isEmpty(ArrayOps.scala:105)
at scala.collection.TraversableLike$class.headOption(TraversableLike.scala:436)
at scala.collection.mutable.ArrayOps$ofRef.headOption(ArrayOps.scala:105)
at com.geeksville.andropilot.service.AndroidDirUpload.send(AndroidDirUpload.scala:42)
at com.geeksville.andropilot.service.AndroidDirUpload.onHandleIntent(AndroidDirUpload.scala:38)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.os.HandlerThread.run(HandlerThread.java:60)