Use master appveyor build status rather than overall status

README.md

@@ -1,7 +1,7 @@
 # tev — The EXR Viewer
 
 [![Travis Build Status](https://travis-ci.org/Tom94/tev.svg?branch=master)](https://travis-ci.org/Tom94/tev)
-[![Appveyor Build Status](https://ci.appveyor.com/api/projects/status/32r7s2skrgm9ubva?svg=true)](https://ci.appveyor.com/project/Tom94/tev)
+[![Appveyor Build Status](https://ci.appveyor.com/api/projects/status/y9pdd25v9b8s5cv1/branch/master?svg=true)](https://ci.appveyor.com/project/Tom94/tev)
 
 A high dynamic range (HDR) image comparison tool for graphics people. __tev__ allows viewing images through various tonemapping operators and inspecting the values of individual pixels. Often, it is important to find exact differences between pairs of images. For this purpose, __tev__ allows rapidly switching between opened images and visualizing various error metrics (L1, L2, and relative versions thereof). To avoid clutter, opened images and their layers can be filtered by keywords.