4.2.1

• Update spotbugs 4.0.1 -> 4.0.2
• Revert (and change) spotbugs configuration customizations:
  • Remove explicit asm dependency for "spotbugs" configuration
    It was added by mistake: dependency-management plugin applied for all configurations
    was actually guilty of incorrect asm version (case description added to documentation)
  • Force correct version of sl4j-simple instead of removing dependency
    (nasty warnings introduced in previous release will disappear now)

Warnings from the previous version are no more actual (except new plugin version (4)).