Remove rust-toolchain file in CI

.travis.yml

@@ -50,6 +50,7 @@ matrix:
     - env: INTEGRATION=hyperium/hyper
 
 script:
+  - rm rust-toolchain
   - cargo install rustup-toolchain-install-master || echo "rustup-toolchain-install-master already installed"
   - travis_retry rustup-toolchain-install-master -f -n master
   - rustup default master

appveyor.yml

@@ -13,6 +13,7 @@ environment:
 
 install:
     - set PATH=C:\Program Files\Git\mingw64\bin;%PATH%
+    - del rust-toolchain
     - curl -sSf -o rustup-init.exe https://win.rustup.rs/
     - rustup-init.exe -y --default-host %TARGET% --default-toolchain nightly
     - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin;C:\Users\appveyor\.rustup\toolchains\nightly-%TARGET%\bin