[xmlunit/xmlunit] 121b53: placeholders change is not backwards compatible

[Stefan B. <no...@gi...>]

  Branch: refs/heads/master
  Home:   https://github.com/xmlunit/xmlunit
  Commit: 121b5350a440348e295924e76639873ed23c6480
      https://github.com/xmlunit/xmlunit/commit/121b5350a440348e295924e76639873ed23c6480
  Author: Stefan Bodewig <ste...@fr...>
  Date:   2020-05-06 (Wed, 06 May 2020)

  Changed paths:
    M .travis.yml
    M RELEASE_NOTES.md
    M pom.xml
    M xmlunit-assertj/pom.xml
    M xmlunit-core/pom.xml
    M xmlunit-legacy/pom.xml
    M xmlunit-matchers/pom.xml
    M xmlunit-placeholders/pom.xml
    M xmlunit-placeholders/src/main/java/org/xmlunit/placeholder/MatchesRegexPlaceholderHandler.java
    M xmlunit-placeholders/src/main/java/org/xmlunit/placeholder/PlaceholderHandler.java

  Log Message:
  -----------
  placeholders change is not backwards compatible

the module has been marked as experimental so making backwards
incompatible changes should be fine, but still we should at least do a
minor release for this.

see #178