Fix appveyor build script

Author: andybarron

appveyor.yml

@@ -109,9 +109,10 @@ install:
 #- ps: .\appveyor_rust_install.ps1 -channel stable -target x86_64-pc-windows-msvc
 
 ## Build Script ##
+build: false # fixes "specify a project or solution file" error
 
 # Uses 'cargo test' to run tests. Alternatively, the project may call compiled programs directly or
 # perform other testing commands. Rust will automatically be placed in the PATH environment
 # variable.
 test_script:
-- cmd: cargo test --verbose
+- cmd: cargo test --verbose