Fix supported Ubuntu version list

Before: Currently, Ubuntu Linux (Server or Desktop) **12.04 LTS** and **13.10** are supported.
After: Currently, Ubuntu Linux (Server or Desktop) **14.04 LTS** and **13.10** are supported.

2014-05-05 21:14:13,651|ERROR: Unsupported Ubuntu version, please use 14.04 LTS or 13.10
rippler@ubuntu:~/counterpartyd_build$ cat /etc/lsb-release