Try to take advantage of travis cache and build stages

.travis.yml

@@ -1,7 +1,10 @@
 language: rust
 rust:
   - nightly-2018-07-17
-cache: cargo
+cache:
+  cargo: true
+  directories:
+  - kcov-master
 sudo: true
 dist: trusty
 
@@ -16,32 +19,36 @@ addons:
       - binutils-dev
       - zlib1g-dev
       - libiberty-dev
+stages:
+  - build
+  - code coverage
 jobs:
   include:
-    - stage: test and build
+    - stage: build
+      name: "Build with postgresql"
+      env:
+        - MIGRATION_DIR=migrations/postgres FEATURES=postgres DATABASE_URL=postgres://postgres@localhost/plume
+      script: cargo build --no-default-features --features="${FEATURES}"
+    - stage: build
+      name: "Build with sqlite"
+      env:
+        - MIGRATION_DIR=migrations/sqlite   FEATURES=sqlite   DATABASE_URL=plume.sqlite3
+      script: cargo build --no-default-features --features="${FEATURES}"
+    - stage: code coverage
+      name: "Calculate code coverage"
       env:
         - RUSTFLAGS='-C link-dead-code'
-      script: cargo test --features sqlite --no-default-features --all
-      after_success:
+      script:
         - |
+            cargo test --features sqlite --no-default-features --all && (
             wget https://github.com/SimonKagstrom/kcov/archive/master.tar.gz &&
             tar xzf master.tar.gz &&
-           cd kcov-master &&
-           mkdir build &&
-           cd build &&
+            mkdir -p kcov-master/build &&
+            cd kcov-master/build &&
             cmake .. &&
             make &&
             sudo make install &&
             cd ../.. &&
-           rm -rf kcov-master &&
             for crate in plume plume_common plume_models plume_api plm lib; do for file in target/debug/$crate-*[^\.d]; do mkdir -p "target/cov/$(basename $file)"; kcov --exclude-pattern=/.cargo,/usr/lib --verify "target/cov/$(basename $file)" "$file"; done; done &&
             bash <(curl -s https://codecov.io/bash) &&
-           echo "Uploaded code coverage"
-    - stage: test and build
-      env:
-        - MIGRATION_DIR=migrations/postgres FEATURES=postgres DATABASE_URL=postgres://postgres@localhost/plume
-      script: cargo build --no-default-features --features="${FEATURES}"
-    - stage: test and build
-      env:
-        - MIGRATION_DIR=migrations/sqlite   FEATURES=sqlite   DATABASE_URL=plume.sqlite3
-      script: cargo build --no-default-features --features="${FEATURES}"
+            echo "Uploaded code coverage" || true )