Add Appveyor badge, test on OS X

Author: dlfivefifty

.travis.yml

@@ -11,7 +11,6 @@ julia:
 matrix:
   allow_failures:
     - julia: nightly
-    - os: osx
 notifications:
   email: false
 after_script:

README.md

@@ -3,6 +3,7 @@
 [![](https://img.shields.io/badge/docs-stable-blue.svg)](https://JuliaApproximation.github.io/ApproxFun.jl/stable)
 [![](https://img.shields.io/badge/docs-latest-blue.svg)](https://JuliaApproximation.github.io/ApproxFun.jl/latest)
 [![Build Status](https://travis-ci.org/JuliaApproximation/ApproxFun.jl.svg?branch=master)](https://travis-ci.org/JuliaApproximation/ApproxFun.jl) 
+[![Build status](https://ci.appveyor.com/api/projects/status/40qmoxp189pwtuda?svg=true)](https://ci.appveyor.com/project/dlfivefifty/approxfun-jl)
 [![codecov](https://codecov.io/gh/JuliaApproximation/ApproxFun.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaApproximation/ApproxFun.jl)
 [![Join the chat at https://gitter.im/JuliaApproximation/ApproxFun.jl](https://badges.gitter.im/JuliaApproximation/ApproxFun.jl.svg)](https://gitter.im/JuliaApproximation/ApproxFun.jl?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)