Convert from Flow to Typescript (#816)

* convert to typescript
* add docs for custom node typing
* update webpack, gulpfile

src/ledger/ledger.ts

@@ -0,0 +1,28 @@
+import {validate} from '../common'
+import parseLedger from './parse/ledger'
+import {GetLedger} from './types'
+
+type LedgerOptions = {
+  ledgerVersion?: number,
+  includeAllData?: boolean,
+  includeTransactions?: boolean,
+  includeState?: boolean
+}
+
+
+function getLedger(options: LedgerOptions = {}): Promise<GetLedger> {
+  validate.getLedger({options})
+
+  const request = {
+    command: 'ledger',
+    ledger_index: options.ledgerVersion || 'validated',
+    expand: options.includeAllData,
+    transactions: options.includeTransactions,
+    accounts: options.includeState
+  }
+
+  return this.connection.request(request).then(response =>
+    parseLedger(response.ledger))
+}
+
+export default getLedger