Update README.rst

Use svg instead of png to get better image quality

README.rst

@@ -3,7 +3,7 @@ CDN Linker for Wordpress and Magento
 ====================================
 .. image:: https://drone.io/github.com/wmark/CDN-Linker/status.png
    :target: https://drone.io/github.com/wmark/CDN-Linker/latest
-.. image:: https://coveralls.io/repos/wmark/CDN-Linker/badge.png?branch=master
+.. image:: https://coveralls.io/repos/wmark/CDN-Linker/badge.svg?branch=master
    :target: https://coveralls.io/r/wmark/CDN-Linker?branch=master
 
 *Info*
@@ -130,4 +130,4 @@ HHVM
   For CDN Linker’s *post-processing* feature you will have to install `hhvm-zmq <//github.com/duxet/hhvm-zmq>`_
   (monitor issue `1214 <//github.com/facebook/hhvm/issues/1214>`_) or resort to Redis.
 
-__ Mark_
+__ Mark_