message: Updating CHANGELOG with news of ex20 and ex20p
diff: Version 3.4.1 (development)
  ===========================
  +New and updated examples and miniapps
  +-------------------------------------
  +
  +- Added a new serial and parallel example (ex20) that solves 1D ordinary
  + differential equations derived from a Hamiltonian. The example
  + demonstrates the use of the variable order, symplectic integration algorithm
  + implemented in SIAVSolver.
  Version 3.4, released on May 29, 2018
  =====================================
  