v1.5.0

• fix the addAnimation() method not returning the corresponding set TrackEntry
• fix the base renderable flip[X/Y] method when used/applied to the Spine renderable
• add a isCurrentAnimation() method that returns true if the given name is corresponding to the current track current animation
• expose the currentTrack property to access the corresponding current animation track entry
• clarify in the readme that the current plugin support both the 4.1 and 4.2-beta Spine runtime versions
• the spine-plugin now requires to be properly registered using me.plugin.register(SpinePlugin);
• the spine-plugin now requires melonJS v15.12.0 or higher
• add check for minimum melonJS version when the plugin is registered
• restructure code to adhere to the updated plugin API and get a proper reference to the melonjs renderer instance