Version 2.0.0 beta-1

• Added tasks into gulp for deploying on production.
• Added new methods named "dateback" and "dateforth".
• Added new option named "effects" for timeline UI enhancement.
• Fixed a bug that does not remove specific events on "removeEvent" method.
• Fixed a bug that the vertical position of the relation line deviates in multiple rows of containers.
• Fixed a bug that method chain did not work due to asynchronous initialization.