Add appveyor to check Windows builds

Author: ismayc

.Rbuildignore

@@ -12,3 +12,4 @@
 ^NEWS\.md$
 ^cran-comments\.md$
 ^_build\.sh$
+^appveyor\.yml$

.gitattributes

@@ -0,0 +1,4 @@
+* text=auto
+data/* binary
+src/* text=lf
+R/* text=lf

README.Rmd

@@ -6,9 +6,7 @@ output: github_document
 
 ------------------------------------------------------------------------
 
-[![CRAN_Status_Badge](http://www.r-pkg.org/badges/version/infer)](https://cran.r-project.org/package=infer)
-[![Travis-CI Build Status](https://travis-ci.org/andrewpbray/infer.svg?branch=master)](https://travis-ci.org/andrewpbray/infer) 
-[![Coverage Status](https://img.shields.io/codecov/c/github/andrewpbray/infer/master.svg)](https://codecov.io/github/andrewpbray/infer/?branch=master)
+[![CRAN_Status_Badge](http://www.r-pkg.org/badges/version/infer)](https://cran.r-project.org/package=infer) [![Travis-CI Build Status](https://travis-ci.org/andrewpbray/infer.svg?branch=master)](https://travis-ci.org/andrewpbray/infer) [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/andrewpbray/infer?branch=master&svg=true)](https://ci.appveyor.com/project/andrewpbray/infer) [![Coverage Status](https://img.shields.io/codecov/c/github/andrewpbray/infer/master.svg)](https://codecov.io/github/andrewpbray/infer/?branch=master)
 
 
 The objective of this package is to perform statistical inference using an expressive statistical grammar that coheres with the `tidyverse` design framework.

appveyor.yml

@@ -0,0 +1,46 @@
+# DO NOT CHANGE the "init" and "install" sections below
+
+# Download script file from GitHub
+init:
+  ps: |
+        $ErrorActionPreference = "Stop"
+        Invoke-WebRequest http://raw.github.com/krlmlr/r-appveyor/master/scripts/appveyor-tool.ps1 -OutFile "..\appveyor-tool.ps1"
+        Import-Module '..\appveyor-tool.ps1'
+
+install:
+  ps: Bootstrap
+
+# Adapt as necessary starting from here
+
+environment:
+  global:
+    WARNINGS_ARE_ERRORS: 1
+
+build_script:
+  - travis-tool.sh install_deps
+
+test_script:
+  - travis-tool.sh run_tests
+
+on_failure:
+  - 7z a failure.zip *.Rcheck\*
+  - appveyor PushArtifact failure.zip
+
+artifacts:
+  - path: '*.Rcheck\**\*.log'
+    name: Logs
+
+  - path: '*.Rcheck\**\*.out'
+    name: Logs
+
+  - path: '*.Rcheck\**\*.fail'
+    name: Logs
+
+  - path: '*.Rcheck\**\*.Rout'
+    name: Logs
+
+  - path: '\*_*.tar.gz'
+    name: Bits
+
+  - path: '\*_*.zip'
+    name: Bits