feeder.go missing some feeder_gateway methods

[D-DePablos]

Commands get_transaction_trace and estimate_fee from starknet (see here) are missing from juno/pkg/feeder/feeder.go as the Starknet Feeder Gateway has been updated to include them.

We should add them along the other avaiable functions for completeness, and to aid #128 and any other integrations which require these functions.