Version 1.8 - May 25 2023, by I. Volobouev

* Added a constructor from two P4 objects to the rk::Boost class.

* Added a few "const" qualifiers to various arguments as appropriate.


Version 1.7 - November 15 2016, by I. Volobouev

* Added methods "beta", "gamma", "betaGamma", and "velocity" to the
  rk::Boost class.

* Added function "rk::transformVelocity".


Version 1.6 - December 16 2014, by I. Volobouev

* Added transverse() function to P4


Version 1.5 - February 28 2013, by I. Volobouev

* Introduced arbitrary Lorentz transformations represented by the "LT"
  class. Internal implementation is via biquaternions which allows for
  a simple transformation renormalization that keeps round-off errors under
  control. Naturally, LT preserves particle masses, just like Boost.


Version 1.4 - July 6 2012, by I. Volobouev

* Changed the deltaPhi function so that it now works for four-vectors.
  As a consequence, deltaR now works as well.


Version 1.3 - April 5 2012, by I. Volobouev

* Added serialization capabilities to all classes by providing the
  "rkIO.hh" header as interface to "Geners".


Version 1.2 - March 1 2011, by I. Volobouev

* Added the rk::Point4 class which can be used to represent space-time
  locations.


Version 1.1 - Oct 2 2010, by I. Volobouev

* Added "peripheralSplit" function. It is declared in the "rk.hh" header.
  This function allows for phase space generation based on sampling
  the Mandelstam t variable ("t-channel" phase space splitting).

* Removed the requirement that all arguments to the kinematic lambda
  function must be positive. This allows for simple calculation of phase
  space weights in recursive t-channel splits.
