Add missing dependency in Kraken exchange
Add missing dependency in Kraken exchange

Added 'moment' dependency. It is required for the retry method which
will crash without it.

generalectric/gekko,WXLWEB/gekko,BarnumD/gekko,pprados/gekko,generalectric/gekko,nourchawich/gekko,pprados/gekko,askmike/gekko,WXLWEB/gekko,WXLWEB/gekko,BarnumD/gekko,askmike/gekko,generalectric/gekko,nourchawich/gekko,pprados/gekko,askmike/gekko,BarnumD/gekko,nourchawich/gekko