add 2in9 example to travis and also check for cargo fmt there

.travis.yml

@@ -104,8 +104,9 @@ script:
   - cargo check  
   - cargo test --all-features --release
   - cargo doc --all-features --release
-  - cd examples/embedded_linux_epd4in2 && cargo check && cd ../../
-  - cd examples/embedded_linux_epd1in54 && cargo check && cd ../../
+  - cd examples/embedded_linux_epd4in2 && cargo fmt --all -- --check && cargo check && cd ../../
+  - cd examples/embedded_linux_epd1in54 && cargo fmt --all -- --check && cargo check && cd ../../
+  - cd examples/embedded_linux_epd2in9 && cargo fmt --all -- --check && cargo check && cd ../../
   # - cd examples/stm32f3discovery && cargo check --target thumbv7m-none-eabi && cd ../../
   #- cd ../f3_stm32f30x && cargo build