v3.7.4

• Improves performance of the reducePositions transform by testing
  against hasOwnProperty instead of using an array of object keys.
• Removes the redundant indexes-of dependency.

v3.7.3

• Unpins postcss-filter-plugins from 2.0.0 as a fix has landed in the new
  version of uniqid.

v3.7.2

• Temporarily pins postcss-filter-plugins to version 2.0.0 in order to
  mitigate an issue with uniqid 3.0.0.

v3.7.1

• Enabling safe mode now turns off both postcss-merge-idents &
  postcss-normalize-url's stripWWW option.

v3.7.0

• Added: Reduce background-repeat definitions; works with both this property
  & the background shorthand, and aims to compress the extended two value
  syntax into the single value syntax.
• Added: Reduce initial values for properties when the actual initial value
  is shorter; for example, min-width: initial becomes min-width: 0.

v3.6.2

• Fixed an issue where cssnano would crash on steps(1).

v3.6.1

• Fixed an issue where cssnano would crash on steps functions with a
  single argument.

v3.6.0

• Added postcss-discard-overridden to safely discard overridden rules with
  the same identifier (thanks to @Justineo).
• Added: Reduce animation/transition timing functions. Detects cubic-bezier
  functions that are equivalent to the timing keywords and compresses, as well
  as normalizing the steps timing function.
• Added the perspective-origin property to the list of supported properties
  transformed by the reduce-positions transform.

v3.5.2

• Resolves an issue where the 3 or 4 value syntax for background-position
  were being incorrectly converted.

v3.5.1

• Improves checking for background-position values in the background
  shorthand property.