Add coverage reporting with kcov

.travis.yml

@@ -1,7 +1,32 @@
 language: rust
+sudo: required
 rust:
   - nightly
   - beta
   - stable
   - 1.14.0 # rustc on debian stable
 cache: cargo
+
+script:
+  - cargo test
+
+deploy:
+  provider: pages
+  skip-cleanup: true
+  github-token: $GITHUB_TOKEN  # Set in the settings page of your repository, as a secure variable
+  keep-history: true
+  local-dir: target/kcov/merged
+  on:
+    branch: master
+    rust: stable
+  script:
+  - mkdir target/kcov target/kcov/unit target/kcov/integration target/kcov/merged
+  - kcov target/kcov/unit target/debug/lightning_invoice-!(*.d)
+  - kcov target/kcov/integration target/debug/ser_de-!(*.d)
+  - kcov target/kcov/unit target/debug/lightning_invoice-!(*.d)
+
+before_install:
+  - sudo apt-get update
+  - sudo apt-get install cmake g++ pkg-config jq libcurl4-openssl-dev libelf-dev libdw-dev binutils-dev libiberty-dev
+  - cargo install cargo-kcov || true
+  - cargo kcov --print-install-kcov-sh | sh