Add code coverage with cargo-tarpaulin and Codecov

.travis.yml

@@ -2,6 +2,12 @@ language: rust
 rust:
   - 1.36.0
 
+addons:
+  apt:
+    packages:
+      # For cargo-tarpaulin
+      - libssl-dev
+
 cache: cargo
 
 before_script:
@@ -9,4 +15,16 @@ before_script:
 
 script:
   - cargo fmt --all -- --check
+  - cargo build --verbose --release --all
   - cargo test --verbose --release --all
+
+before_cache:
+  - rm -rf "$TRAVIS_HOME/.cargo/registry/src"
+  - cargo install cargo-tarpaulin || echo "cargo-tarpaulin already installed"
+  - cargo install cargo-update || echo "cargo-update already installed"
+  - cargo install-update -a # update outdated cached binaries
+
+after_success:
+  # Manually exclude packages that are going to be removed from the workspace
+  - travis_wait cargo tarpaulin --release --timeout 600 --out Xml --packages "librustzcash,zcash_client_backend,zcash_primitives,zcash_proofs"
+  - bash <(curl -s https://codecov.io/bash)