travis: Build stmhal/ST32F4DISC and teensy in Travis tests.

.travis.yml

@@ -15,6 +15,8 @@ script:
   - make -C bare-arm
   - make -C qemu-arm
   - make -C stmhal
+  - make -C stmhal BOARD=STM32F4DISC
+  - make -C teensy
   - make -C windows CROSS_COMPILE=i586-mingw32msvc-
 
   - (cd tests && MICROPY_CPYTHON3=python3.3 ./run-tests)