Add asynchronous versions of existing methods that support callbacks

[miafan23]

Added async version of following methods:

• All native methods
  • listTablesAsync
  • describeTableAsync
  • batchGetItemAsync
  • batchWriteItemAsync
  • deleteItemAsync
  • getItemAsync
  • putItemAsync
  • updateItemAsync
• dynoExtensions
  • createTableAsync
  • deleteTableAsync
  • queryAsync
  • scanAsync

[miafan23]

Added tests for all async methods! Back to you @AlexanderBelokon