Remove redundant +nightly specifiers

.travis.yml

@@ -46,8 +46,8 @@ jobs:
     os: osx
     osx_image: xcode9.4
     rust: nightly
-    install: rustup +nightly component add rust-src
-    script: cargo +nightly test -Z build-std --target i686-apple-darwin --verbose
+    install: rustup component add rust-src
+    script: cargo test -Z build-std --target i686-apple-darwin --verbose
 
   - name: Linux stable
     os: linux
@@ -60,7 +60,7 @@ jobs:
     os: osx
     osx_image: xcode7.3
     rust: nightly
-    before_install: rustup +nightly component add rust-src
+    before_install: rustup component add rust-src
     install: curl -LO https://github.com/SSheldon/rust-test-ios/releases/download/0.1.1/rust-test-ios && chmod +x rust-test-ios
     before_script: echo "[unstable]\nbuild-std = []" > $HOME/.cargo/config.toml
     env: FEATURES="exception"