Added appveyor.yml to enable integration with Appveyor (#155)

appveyor.yml

@@ -0,0 +1,10 @@
+clone_folder: c:\go\src\github.com\google\pprof
+
+before_build:
+ - go get github.com/ianlancetaylor/demangle
+
+build_script:
+ - go build github.com/google/pprof
+
+test_script:
+  - go test ./...