add travis-ci and appveyor build status

README.md

 # QGroundControl
 ## Open Source Micro Air Vehicle Ground Control Station
 
+[![Travis Build Status](https://travis-ci.org/mavlink/qgroundcontrol.svg?branch=master)](https://travis-ci.org/mavlink/qgroundcontrol)
+[![Appveyor Build Status](https://ci.appveyor.com/api/projects/status/crxcm4qayejuvh6c/branch/master?svg=true)](https://ci.appveyor.com/project/mavlink/qgroundcontrol)
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@@ -162,4 +165,4 @@ Connexion's 3D mice are supported through the 3DxWARE driver available on Linux
 ### XBee support
 QGroundControl can talk to XBee wireless devices using their proprietary protocol directly on Windows and Linux platforms. This support is not necessary if you're not using XBee devices or aren't using their proprietary protocol. On Windows, the necessary dependencies are included in this repository and no additional steps are required. For Linux, change to the `libs/thirdParty/libxbee` folder and run `make;sudo make install` to install libxbee on your system (uninstalling can be done with a `sudo make uninstall`). `qmake` will automatically detect the library on Linux, so no other work is necessary.
 
-To disable XBee support you may add `DISABLE_XBEE` to the DEFINES argument.
\ No newline at end of file
+To disable XBee support you may add `DISABLE_XBEE` to the DEFINES argument.