Fix `cos/angle(from:)` for zero vectors

• Swift 4.2 and Xcode 10
• Renamed APIs
  • cos(angleFrom:) to cos(from:)
  • nealyEqual to isNealyEqual
• Support CGVector
• Add missing APIs
  • New operators
    • *(CGPoint, CGPoint) -> CGPoint, /(CGPoint, CGPoint) -> CGPoint
    • *=(inout CGPoint, CGPoint), /=(inout CGPoint, CGPoint)
    • Operators for mixed types
  • Full vector APIs for CGSize and CGVector same as CGPoint
• Remove CGAffineTransform.inverse

Changes from 0.3.0-beta.2

• Fix cos/angle(from:) for zero vectors