How to upgrade from ionic framework 1.2.4 to 1.31

I’d like to upgrade from ionic framework 1.2.4 to 1.3.1. I run the following command:

ionic lib update

Got the following error message:

This command has been deprecate. All resources are currently available in NPM and we recommend that you use NPM to manage these.
More information is available here: https://github.com/driftyco/ionic-cli/wiki/Migrating-to-NPM-from-bower

Are you sure you want to replace /Users/zhouhao/Desktop/client/www/lib/ionic with an updated version of Ionic?
(yes/no): yes
Invalid version: undefined

Then I change my bower.json:

  "devDependencies": {
    "ionic": "driftyco/ionic-bower#1.3.1",
    "ionic-platform-web-client": "~0.2.1"
  },

And run:

bower update ionic

Got the following error:

bower skipped ionic was not installed because there is already a non-bower directory with that name in the components directory (www/lib/ionic). You can force installation with --force.

What should I do? Thanks

bower update ionic --force

Seems solve the problem.