Bugfixes:

• #22 Fix scrolling issue

• Add events for lifecycles
• Add custom classes

• Fixed scrolling issue on mobile devices

• Fixed issue where user couldn't click on div element inside dad container
• Added support for children exchange between containers
• Removed addDropzone method once the feature above covers it
• Added support for placeholder customization
• Added custom events to handle element dropping
• Refactored code

• Drag/drop DOM elements
• Activate/deactivate container
• Add callback on drop
• Set target element within the container
• Compatible with bootstrap