[DOC] Add API.md listing all routes.
[DOC] Add subheaders for each api call.
[DOC] Began adding subheaders for api calls.
[DOC] Finish adding method, url as subheaders.
[DOC] Add first few json request, responses.
[DOC] Format API doc.
[DOC] Add more api endpoint json responses.
[DOC] Add short description for each api call.
[DOC] Add API docs to README.
[DOC] Add more api json.
[CHORE] Make user_auth part of webapp config.
Merge pull request #125 from ripple/api-doc

Api doc
[FIX] Record to_address_id not from_address_id.
[FEATURE] Refactor out WithdrawalProcessor.
[FIX] Use proper state field for predicate.