Convert from Flow to Typescript (#816)

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

src/ledger/parse/escrow-execution.ts

@@ -0,0 +1,17 @@
+import * as assert from 'assert'
+import {parseMemos} from './utils'
+import {removeUndefined} from '../../common'
+
+function parseEscrowExecution(tx: any): Object {
+  assert(tx.TransactionType === 'EscrowFinish')
+
+  return removeUndefined({
+    memos: parseMemos(tx),
+    owner: tx.Owner,
+    escrowSequence: tx.OfferSequence,
+    condition: tx.Condition,
+    fulfillment: tx.Fulfillment
+  })
+}
+
+export default parseEscrowExecution