Update travis

Author: Zibi Braniecki

.travis.yml

@@ -16,5 +16,7 @@ script:
 - cargo test
 
 after_success: |
-  bash <(curl https://raw.githubusercontent.com/xd009642/tarpaulin/master/travis-install.sh)
-  cargo tarpaulin --ciserver travis-ci --ignore-tests --coveralls $TRAVIS_JOB_ID
+  if [[ "$TRAVIS_RUST_VERSION" == stable ]]; then
+    RUSTFLAGS="--cfg procmacro2_semver_exempt" cargo install cargo-tarpaulin
+    cargo tarpaulin --ciserver travis-ci --coveralls $TRAVIS_JOB_ID
+  fi