Explain Travis CI usage

Closes #2432

Author: phansch

README.md

@@ -64,6 +64,20 @@ rustup component add clippy-preview
 
 Now you can run Clippy by invoking `cargo clippy`.
 
+#### Travis CI
+
+You can add Clippy to Travis CI in the same way you use it locally:
+
+```yml
+- rust: stable
+  before_script:
+    - rustup component add clippy-preview
+  script:
+    - cargo clippy
+    - cargo test
+    # etc.
+```
+
 ### Running Clippy from the command line without installing it
 
 To have cargo compile your crate with Clippy without Clippy installation