added option to only write out files that have unused dependencies
removed unnecessary check for results.length > 0
changed option name to saveFilesWithUnusedDependenciesOnly and documented in README

changed option name to saveFilesWithUnusedDependenciesOnly

added documentation for saveFilesWithUnusedDependenciesOnly
Merge pull request #5 from tomwayson/master

added option to only write out files that have unused dependencies