Bugfix#15 update data uploader to create columns with correct datatype in dynamo db

[senthilkumarmohan]

Fix for Issue #15

• Refactored code to build DynamopDB attributes into a separate function.
• Updated code to create columns with correct data type.
• Added checks to map float data type to DynamoDB's Number type.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.