[TASK] rename fee endpoint to `/transaction-fee`
[TASK] add `max_transaction_fee` to config

so a user can configure the `max_transaction_fee` on a remote, how much they're willing to pay in fees per transaction
Merge pull request #209 from geertweening/config_max_fee

[TASK] add `max_fee` to config
[TASK] bump ripple-lib to 0.9.3-rc3
Merge pull request #204 from geertweening/rename_fee_endpoint

[TASK] rename fee endpoint to `/transaction-fee`
[TEST] add tests for source currencies query parameter for path find route
Merge pull request #210 from boxbag/pathfind-source-currencies-test

[TEST] add tests for source currencies query parameter for path find route