Modify ruby Makefile to use bundler to resolve dependencies.
Modify coffeescript Makefile to use npm to resolve dependencies.
calculate_seconds_since_datetime/check verifies the output
Remove node_modules when package.json has changed because npm install
doesn't clear out old packages or versions.
Modify calculate_seconds_since_datetime/ruby to pass the test.
Implement calculate_seconds_since_datetime/coffeescript