ci: add node@10, small fixes

Author: nodkz

.eslintignore

@@ -1,2 +1,3 @@
 flow-typed/*
 lib/*
+postinstall.js

.travis.yml

@@ -8,6 +8,7 @@ cache:
 notifications:
   email: true
 node_js:
+  - "10"
   - "9"
   - "8"
 before_install: yarn global add greenkeeper-lockfile@1

postinstall.js

@@ -8,11 +8,13 @@ It helps to skip timeout setup `jasmine.DEFAULT_TIMEOUT_INTERVAL = 60000;`
 when first test run hits MongoDB binary downloading to the cache.
 */
 
-const MongoBinary = require('./lib/util/MongoBinary').default;
+if (require.resolve('./lib/util/MongoBinary')) {
+  const MongoBinary = require('./lib/util/MongoBinary').default;
 
-console.log('mongodb-memory-server: checking MongoDB binaries cache...');
-MongoBinary.getPath({
-  version: 'latest',
-}).then(binPath => {
-  console.log(`mongodb-memory-server: binary path is ${binPath}`);
-});
+  console.log('mongodb-memory-server: checking MongoDB binaries cache...');
+  MongoBinary.getPath({
+    version: 'latest',
+  }).then(binPath => {
+    console.log(`mongodb-memory-server: binary path is ${binPath}`);
+  });
+}