package.json,bin/slush.js: Bump to liftoff 2.5.0

Fixes the "should fail when running a generator without slushfile" test
case.

As noted in the commit that updated runSlush() from test/slush.js and
caused the failure, slush was actually failing without the expected "No
slushfile found" message. It was failing with a stack trace that
started with:

  path.js:39
      throw new ERR_INVALID_ARG_TYPE('path', 'string', path);
    ^

  TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type
  string. Received type object
      at assertPath (path.js:39:11)
      at Object.extname (path.js:1375:5)
      at Liftoff.buildEnvironment (/Users/mbland/src/mbland/slush/node_modules/liftoff/index.js:111:50)
      at Liftoff.launch (/Users/mbland/src/mbland/slush/node_modules/liftoff/index.js:154:22)
      at Object.<anonymous> (/Users/mbland/src/mbland/slush/bin/slush.js:57:5)

This points to a bug in the previous version of liftoff whereby the the
search for `slushfile.js` found nothing, resulting in a `configPath` of
`null`. liftoff passed this `null` to `Object.extname`, resulting in
this stack trace.

liftoff v2.5.0 doesn't have this problem, but it does have a slightly
different API. With the changes to `bin/slush.js`, this test case now
passes along with the rest of the suite.

Author: Bland, Mike

bin/slush.js

@@ -16,6 +16,7 @@ var versionFlag = argv.v || argv.version;
 var params = argv._.slice();
 var generatorAndTasks = params.length ? params.shift().split(':') : [];
 var generatorName = generatorAndTasks.shift();
+var tasks = generatorAndTasks;
 
 if (!generatorName) {
   if (versionFlag) {
@@ -34,11 +35,6 @@ if (!generator) {
   process.exit(1);
 }
 
-// Setting cwd and slushfile dir:
-argv.cwd = process.cwd();
-argv.slushfile = path.join(generator.path, 'slushfile.js');
-argv._ = generatorAndTasks;
-
 var cli = new Liftoff({
   processTitle: 'slush',
   moduleName: 'gulp',
@@ -54,13 +50,14 @@ cli.on('requireFail', function(name) {
   gutil.log(chalk.red('Failed to load external module'), chalk.magenta(name));
 });
 
-cli.launch(handleArguments, argv);
+cli.launch({
+  // Setting cwd and slushfile dir:
+  cwd: process.cwd(),
+  configPath: path.join(generator.path, 'slushfile.js')
+}, handleArguments);
 
 function handleArguments(env) {
-
-  var argv = env.argv;
   var tasksFlag = argv.T || argv.tasks;
-  var tasks = argv._;
   var toRun = tasks.length ? tasks : ['default'];
   var args = params;
 

package.json

@@ -28,7 +28,7 @@
     "gulp-util": "^2.2.0",
     "pretty-hrtime": "^1.0.3",
     "archy": "^1.0.0",
-    "liftoff": "~0.10.0",
+    "liftoff": "^2.5.0",
     "chalk": "^2.4.1"
   },
   "devDependencies": {