$ sudo apt-get update #Don't get any errors
$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
$ sudo update-manager -d
Ubuntu checks for updates, tells me my computer is up to date. But there are only two options now "Ok" and "Settings". According to this and several other websites, there should be an option to upgrade it to 14.04, but I'm seeing none. How can I upgrade to 14.04?