Update node versions to match real usage, and handle node 8 issues

Production uses 10.15.1, so it'd be better to test with that, not
10.15.3. 8 is marked as technically supported, but doesn't have
fs.promises. It's still mostly functional, so we'll preserve that
for now, but it's very likely that future versions will drop this.
In the meantime, we just avoid breaking immediately for 8.

Author: pimterry

.travis.yml

@@ -4,7 +4,7 @@ language: node_js
 node_js:
 - node
 - '12'
-- '10.15.3'
+- '10.15.1'
 - '8'
 before_install:
 - sudo apt-get install p7zip-full xterm
@@ -25,7 +25,7 @@ addons:
 jobs:
   include:
     - stage: Build and release binaries
-      node_js: '10.15.3'
+      node_js: '10.15.1'
       echo: 'Building binaries...'
       script:
         - |

src/commands/start.ts

@@ -58,6 +58,8 @@ class HttpToolkitServer extends Command {
 
     // On startup, we want to kill any downloaded servers that are not longer necessary
     async cleanupOldServers() {
+        if (!fs) return; // In node 8, fs.promises doesn't exist, so just skip this
+
         const { dataDir, version: currentVersion } = this.config;
 
         const serverUpdatesPath = process.env.OCLIF_CLIENT_HOME ||