.travis.yml: Skip setting build environment variables.
.travis.yml: Skip setting build environment variables.

jakirkham/rank_filter,DudLab/rank_filter,DudLab/rank_filter,jakirkham/rank_filter,jakirkham/rank_filter,nanshe-org/rank_filter,nanshe-org/rank_filter,nanshe-org/rank_filter,DudLab/rank_filter