Use TypeScript project reference (#1002)

* Add *.tsbuildinfo to .gitignore

* Bump versions of dependencies, nyc and yargs

* Drop support for node 9 (EOL 2018-06-30)

https://github.com/nodejs/Release

* Add getTransaction snippet

snippets/src/getTransaction.ts

@@ -0,0 +1,17 @@
+import {RippleAPI} from '../../dist/npm'
+
+const api = new RippleAPI({
+  server: 'wss://s.altnet.rippletest.net:51233'
+})
+
+getTransaction()
+
+async function getTransaction() {
+  await api.connect()
+  const ledger = await api.getLedger({includeTransactions: true})
+  console.log(ledger)
+  const tx = await api.getTransaction(ledger.transactionHashes[0])
+  console.log(tx)
+  console.log('deliveredAmount:', tx.outcome.deliveredAmount)
+  process.exit(0)
+}