[DOC] add doc that accountRequest throws
[DOC] add doc that accountRequest throws

if a marker is provided, but no ledger_index or ledger_hash 

ripple/ripple-lib,ripple/ripple-lib,wilsonianb/ripple-lib,wilsonianb/ripple-lib,wilsonianb/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,darkdarkdragon/ripple-lib