added tests for the examples to travis

.travis.yml

@@ -82,6 +82,9 @@ matrix:
     #  os: osx
     #  rust: nightly
 
+    - env: TEST_DIR=examples/embedded_linux
+    #- env: TEST_DIR=examples/f3_stm32f30x
+
 before_install:
   - set -e
   - rustup self update
@@ -97,6 +100,7 @@ script:
   - cargo test
   - cargo test --release
   - cargo doc --release
+  - cd $TEST_DIR && cargo build
 
 after_success:
   - cargo doc-upload