Remove deprecated gulp-util by updating gulp-header & gulp-footer

[simonua]

#149 in this repo recently removed its own immediate dependencies on gulp-util, but npm ls gulp-util shows remaining dependencies for gulp-header and gulp-footer. These dependencies were updated today to remove the deprecated gulp-util, so we should update them here in order to rid gulp-angular-templatecache of gulp-util entirely.

[simonua]

Referencing the gulp-util ecosystem migration ticket.

[betorobson]

Hi, any update about this issue?

[tiberiuzuld]

+1