update travis

Author: tafia

.travis.yml

@@ -9,17 +9,9 @@ rust:
 
 before_script:
   - export PATH=$HOME/.cargo/bin:$HOME/.local/bin:$PATH
-  - pip install -v 'travis-cargo<0.2' --user
-  - travis-cargo --only nightly install rustfmt-nightly -- --force
+  - rustup component add rustfmt-preview
 
 script:
-  - travis-cargo --only nighlty fmt -- --write-mode=diff
+  - cargo +nightly fmt -- --write-mode=diff
   - cargo build
   - cargo test
-  - travis-cargo --only stable doc
-after_success:
-  - travis-cargo --only stable doc-upload
-
-env:
-  global:
-    - TRAVIS_CARGO_NIGHTLY_FEATURE=""