Updated Travis

- Added 2nd example
- use cargo check instead of cargo build for first fast check

.travis.yml

@@ -95,12 +95,13 @@ install:
   - rustup override set nightly
 
 script:
-  - cargo build
+  - cargo check
   - cargo build --release
   - cargo test
   - cargo test --all-features --release
   - cargo doc --all-features --release
-  - cd examples/embedded_linux_epd4in2 && cargo build && cd ../../
+  - cd examples/embedded_linux_epd4in2 && cargo check && cd ../../
+  - cd examples/embedded_linux_epd1in54 && cargo check && cd ../../
   #- cd ../f3_stm32f30x && cargo build
 
 after_success: