fix appveyor build

Author: little-dude

.appveyor.yml

@@ -0,0 +1,17 @@
+environment:
+  matrix:
+  - TARGET: x86_64-pc-windows-msvc
+  - TARGET: i686-pc-windows-msvc
+  - TARGET: x86_64-pc-windows-gnu
+  - TARGET: i686-pc-windows-gnu
+  RUST_BACKTRACE: full
+install:
+  - curl -sSf -o rustup-init.exe https://win.rustup.rs/
+  - rustup-init.exe -y --default-host %TARGET%
+  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
+  - rustc -vV
+  - cargo -vV
+build: false
+test_script:
+  - cargo build --verbose --features yaml
+  - cargo test --verbose --features yaml