Update or remove gulp-util dependency

[dwighthouse]

gulp-util has been deprecated. When attempting to install gulp-hash-filename, the following message is displayed:

npm WARN deprecated gulp-util@3.0.8: gulp-util is deprecated - replace it, following the guidelines at https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5

From what I can see in the codebase, you aren't actually using it. There are four locations where you import it, but then you never use the imported gutil variable.

[dwighthouse]

PR created: #7

[intervalia]

Resolved in Version 2.0.1