Test files in this repository for correct formatting during CI build

Build fails from:
- Trailing whitespace
- True tabs
- No newline at end of file

.travis.yml

@@ -43,6 +43,13 @@ before_install:
   # Check for issues in the script
   - bash -c 'shopt -s globstar; shellcheck arduino-ci-script.sh'
 
+  # Check for trailing whitespace in all files in the repository
+  - "if grep --line-number --recursive --exclude-dir=.git '[[:blank:]]$' .; then echo 'Trailing whitespace found.'; false; fi"
+  # Check for tabs in all files in the repository
+  - "if grep --line-number --recursive --exclude-dir=.git $'\t' .; then echo 'Tab found.'; false; fi"
+  # Check if all files in the repository end in a newline (https://stackoverflow.com/a/25686825)
+  - find . -path ./.git -prune -o -type f -print0 | xargs -0 -L1 bash -c 'if test "$(tail --bytes=1 "$0")"; then echo "No new line at end of $0"; false; fi'
+
   - source "${TRAVIS_BUILD_DIR}/arduino-ci-script.sh"
 
   - set_script_verbosity "$VERBOSITY_LEVEL"