Update circle.yml to use the current ubuntu 14.04 python version. (#709)
Update circle.yml to use the current ubuntu 14.04 python version. (#709)

This prevents circleci from downloading the old version, patching it,
and compiling it every time integration tests run.
dmpiergiacomo/scion,FR4NK-W/osourced-scion,dmpiergiacomo/scion,dmpiergiacomo/scion,klausman/scion,klausman/scion,netsec-ethz/scion,dmpiergiacomo/scion,netsec-ethz/scion,dmpiergiacomo/scion,Oncilla/scion,Oncilla/scion,FR4NK-W/osourced-scion,FR4NK-W/osourced-scion,netsec-ethz/scion,Oncilla/scion,FR4NK-W/osourced-scion,Oncilla/scion,klausman/scion,klausman/scion,FR4NK-W/osourced-scion,netsec-ethz/scion,klausman/scion,dmpiergiacomo/scion