* Added a new table 'mib' with 'data', 'size' and 'method' columns
* added AddMIB() function and test case TestMIBHappyPath()
* added function and a test case to add entries into bandwidth usage table
* added functionality to create an entry, update the entry and readback the entry based on a given date into/from bandwidth tbl
* added initial SumBandwidthSizes()
* added the functionality to retrieve the total bw usage based on start and end date
* Added the unit test case for AddBwUsageTbl
* changed the arguments to take time format as arg than Unix format
* changed the arguments to take time format as arg than Unix format
* changes per code review comments
* adding back go.sum
* changes per code review comments
* changes per code review comments
* changes per code review comments
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