Travis: ShellCheck kaleidoscope-builder

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

.travis.yml

@@ -2,10 +2,15 @@ dist: trusty
 sudo: false
 os:
   - linux
+addons:
+  apt:
+    packages:
+      - shellcheck
 install:
   - git clone --depth 1 --recurse-submodules https://github.com/keyboardio/Arduino-Boards hardware/keyboardio/avr
 script:
   - make travis-test BOARD_HARDWARE_PATH=$(pwd)/hardware
+  - shellcheck bin/kaleidoscope-builder
 notifications:
   irc:
     channels: