add shields.io status badges [skip ci]

Author: skvark

README.rst

@@ -1,10 +1,5 @@
-+-------------+------------------+
-| Platform    | Status           |
-+=============+==================+
-| Windows     | |buildstatus|    |
-+-------------+------------------+
-| Manylinux   | |Build Status|   |
-+-------------+------------------+
+.. image:: https://img.shields.io/appveyor/ci/skvark/opencv-python.svg?maxAge=2592000&label=Windows   :target: https://travis-ci.org/skvark/opencv-python
+.. image:: https://img.shields.io/travis/skvark/opencv-python.svg?maxAge=2592000&label=Linux   :target: https://travis-ci.org/skvark/opencv-python
 
 OpenCV on wheels
 ================