Update Travis config

.travis.yml

@@ -1,9 +1,50 @@
 language: rust
+cache: cargo # https://docs.travis-ci.com/user/caching/#Rust-Cargo-cache
 
-before_script:
-  - pip install 'travis-cargo' --user && export PATH=$HOME/.local/bin:$PATH
+rust:
+  - stable
+  - beta
+
+matrix:
+  # Since this item is allowed to fail, don't wait for it's result to mark the
+  # build complete.
+  fast_finish: true
+  allow_failures:
+    - env: NAME='nightly'
+    - env: NAME='kcov'
+  include:
+    - env: NAME='nightly'
+      rust: nightly
+    - env: NAME='rustfmt'
+      rust: nightly
+      before_script:
+        - rustup component add rustfmt-preview
+      script:
+        - cargo fmt --all -- --write-mode=diff
+    - env: NAME='kcov'
+      sudo: required # travis-ci/travis-ci#9061
+      before_script:
+        - cargo install cargo-update || echo "cargo-update already installed"
+        - cargo install cargo-kcov || echo "cargo-kcov already installed"
+        - cargo install-update -a
+      script:
+        - cargo kcov --print-install-kcov-sh | sh
+        - cargo update # Creates `Cargo.lock` needed by next command
+        - cargo kcov --verbose --features dss --coveralls -- --verify --exclude-pattern=/.cargo,/usr/lib,src/proto
+      addons:
+        apt:
+          packages:
+            - libcurl4-openssl-dev
+            - libdw-dev
+            - binutils-dev
+            - libiberty-dev
+            - zlib1g-dev
+
+env:
+  global:
+  - RUSTFLAGS="-C link-dead-code"
 
 script:
-  - |
-      travis-cargo build &&
-      travis-cargo test
+  - cargo build --verbose --all-features
+  - cargo test --verbose --all-features
+  - cargo doc --verbose --all-features --no-deps