1.0.0

What's Changed

• Update Version 1.0.0 by @metaone01 in #4
  bugfix:Units.FontSize(em) cannot get correct value
  bugfix: RelativelengthMerge cannot work properly.
  feat: Custom property bindings.
  feat: RelativeLength calculation (can only be set in code behind currently)
  refactor: Interface IRelativeLength has been refactored to abstract class RelativeLengthBase.
  feat: Added RelativeLengthSub for RelativeLength's subtractions.
  breaking changes.
  update: unittest.
  feat:Now can add/subtract RelativeLengths in axaml.
  breaking change: Changed the RelativeXXXChanged event.
  feat:SetOneTimeWidth
  feat:SetOneTimeHeight
  feat:CalcRelative
  docs
  update: Add unittests for SetOneTimeWidth and SetOneTimeHeight.
  update: Add demo.

Full Changelog: 0.2.1...1.0.0