Messaging API - August 2020 update

[tkgauri]

News: https://developers.line.biz/en/news/2020/08/04/messaging-api-update-august-2020/

• Unsend event has been added
• Video viewing complete event has been added
• The audiences property is now optional instead of required for a certain endpoint
• Create audience for uploading user IDs (by file)
• Add user IDs or Identifiers for Advertisers (IFAs) to an audience for uploading user IDs (by file

[kkdai]

#223 for the unsend and video viewing complete

[justdomepaul]

@tkgauri @kkdai

My commit is finish managing audience api sdk in this pr and issue#194

Maybe it can help to resolve issue

• The audiences property is now optional instead of required for a certain endpoint
• Create audience for uploading user IDs (by file)
• Add user IDs or Identifiers for Advertisers (IFAs) to an audience for uploading user IDs (by file

Please to review pull request and code review to make sure code have quality.