v2.8.9

• Deprecated Protobuf::Lifecycle module in favor of using ActiveSupport::Notifications. [#139, @devin-c]
• Modify $LOAD_PATH inside descriptors.rb to make it easier for other libraries to write their own compiler plugins using our pre-compiled descriptors. [#141, @localshred]
• Add protobuf:clean and protobuf:compile rake tasks for use in external libraries to compile source definitions to a destination. [#142, @localshred]