BUG mixin keyframes at helpers.scss

[pedromarquesm]

Don't forget the #{$string }

Original code just had $animation-name, what caused the scss file to convert it as a name and not a variable, having no animations working on the app

@mixin keyframes($animation-name) {
  @-webkit-keyframes #{$animation-name} {
    @content;
  }
  @-moz-keyframes #{$animation-name} {
    @content;
  }
  @keyframes #{$animation-name} {
    @content;
  }
}