[FIX] change handling of requestLedger options

ledger_index and ledger_hash were being set to true
instead of the specified value, and according to API
docs 'closed','validated', and 'current' can be
supplied to the ledger_index field to get the most
recent of the specified type
Merge pull request #176 from shekenahglory/develop

[FIX] change handling of requestLedger options
configurable maxAttempts
Merge pull request #178 from ripplerm/develop

configurable maxAttempts
[FEATURE] make maxLoops in seed.get_key optional

default to 1 or the index of the requested account +1
[FEATURE] identity functions
[CHORE] vault client: add type to attest parameters
[TASK] vault client: add parameters to attest
[TASK] switch to new attestation endpoint
[FEATURE] vault client: update attestation and attestation summary
[TASK] vault client: tests for attestation routes and full summary
Merge pull request #181 from shekenahglory/feature/identity

Feature/identity
[DOC] update release notes
[TASK] bump version to 0.8.3-rc1
[FIX] vault client: URI decode attestation token
Merge pull request #182 from shekenahglory/fix/attestation

[FIX] vault client: URI decode attestation token
Merge pull request #179 from geertweening/develop

[FEATURE] make maxLoops in seed.get_key() optional
[DOC] update release notes
[TASK] bump version to 0.9.0-rc1
[FEATURE] add flag to show or hide interest in to_human/to_json

The show_interest flag will default to true for interest bearing currencies and false for currencies without interest