travis: test on Windows (nodejs#719)

Run CI on Windows.

.travis.yml

@@ -2,6 +2,7 @@ language: node_js
 os:
   - linux
   - osx
+  - windows
 node_js:
   - '11'
   - '10'

lib/spawn.js

@@ -12,7 +12,13 @@ function spawn(cmd, args, options) {
       args = [cmd].concat(args);
       cmd = process.execPath;
     } else {
-      args = ['/c', cmd].concat(args);
+      // The /C option is capitalized to make tests work. Specifically, this
+      // allows to bypass an issue in https://github.com/tapjs/spawn-wrap used
+      // by https://github.com/istanbuljs/nyc to track code coverage.
+      // The problem is that `mungeCmd()` (
+      // https://github.com/tapjs/spawn-wrap/blob/7931ab5c/index.js#L143)
+      // incorrectly replaces `spawn()` args.
+      args = ['/C', cmd].concat(args);
       cmd = 'cmd';
     }
   }

package.json

@@ -17,7 +17,7 @@
     "coverage": "npm run tap -- --coverage",
     "coverage-html": "npm coverage -- --coverage-report=html",
     "lint": "eslint bin/* lib/ test/ --cache",
-    "tap": "tap -J --timeout 240 \"test/**/test-*.js\"",
+    "tap": "tap -J --timeout 480 \"test/**/test-*.js\"",
     "test": "npm run lint && npm run tap",
     "test-ci": "npm run lint && npm run coverage -- --coverage-report=lcov"
   },

test/test-spawn.js

@@ -54,7 +54,7 @@ test('spawn: windows mock', (t) => {
   const result = spawn('echo', ['Hello world.']);
   const expected = {
     cmd: 'cmd',
-    args: ['/c', 'echo', 'Hello world.'],
+    args: ['/C', 'echo', 'Hello world.'],
     options: undefined
   };