Turning in Build Tools assignment.

Turning in Build Tools assignment.
Thank you for your review! Fixed as https://github.com/HIROSN/build-tools/commit/1a140adc79aa7185073dc4848273fb331711d03c#diff-35b4a816e0441e6a375cd925af50752c (Travis https://travis-ci.org/HIROSN/build-tools/builds/42557595)