Ansible builds for ubuntu are available in PPA. That means all you need to do is add PPA to you repo's and then use ubuntu's default package installer (apt-get).
To configure the PPA on your machine and install ansible run these commands:
$ sudo apt-get install software-properties-common
$ sudo apt-add-repository ppa:ansible/ansible
$ sudo apt-get update
$ sudo apt-get install ansible
You can also install via pip as below:
$ sudo pip install ansible