CHANGELOG.md: The statement about the support situation of MRIv2.0 was changed.
  For MRIv2.0 with patchlevel lower than 451, the function is
  succeedingly offered not using NativeExtension but using TracePointAPI which
  Ruby offers.
  It is because corresponding to set_trace_func having stopped returning
  binding information by change of Ruby.
Merge pull request #16 from ygotoh/mod-CHANGELOG.md

CHANGELOG.md: The statement about the support situation of MRIv2.0 was changed.