Starting to add append to dataset for api.
Adding append to data sets through the api, contribution keys and email/pass accepted
Making rubocop happy.
Addresses issue #1417
Merge pull request #1430 from jdalphon/appendToDataSet

Append to data set
Merge pull request #1431 from JKinsman1993/jk1417_validate_contrib_keys

Addresses issue #1417