'caching' animations using placeholders so that every property is generated only once

_animations.css.sass

%transition-delay
  -webkit-transition-delay: $default-transition-delay
  -moz-transition-delay: $default-transition-delay
  -o-transition-delay: $default-transition-delay
  transition-delay: $default-transition-delay

%transition-duration
  -webkit-transition-duration: $default-transition-duration
  -moz-transition-duration: $default-transition-duration
  -o-transition-duration: $default-transition-duration
  transition-duration: $default-transition-duration
  
%transition-timing
  -webkit-transition-timing-function: $default-transition-function
  -moz-transition-timing-function: $default-transition-function
  -o-transition-timing-function: $default-transition-function
  transition-timing-function: $default-transition-function

%animate-background-color
  @include transition-property(background-color)
  @extend %transition-duration
  @extend %transition-timing

%animate-border-color
  @include transition-property(border-color)
  @extend %transition-duration
  @extend %transition-timing