[OMID-64] Fix location of protobuf tgz in travis config
[OMID-64] Fix location of protobuf tgz in travis config

Location has changed to
https://github.com/google/protobuf/releases/download/v2.5.0/protobuf-2.5.0.tar.gz

Change-Id: Icd7740ff23bf17142fb47bdc530178b0292b3a05

yonigottesman/incubator-omid,yonigottesman/incubator-omid