v0.2.0

• added a second initializer to PASTAPattern
• integrated Metron
  • replaced several geomtric computations with Metrons implementations
  • functions which return an angle as CGFloat now returns Angle
• fixed a bug where marker snapshot was not updated
• extended PASTAPattern / MarkerSnapshot with CustomDebugStringConvertible
• added test_spec to podspec and some unit tests
• Readme updated with "How To Use" section