Fix python versions in travis config
Fix python versions in travis config

liorvh/grab,huiyi1990/grab,kevinlondon/grab,shaunstanislaus/grab,alihalabyah/grab,raybuhr/grab,kevinlondon/grab,raybuhr/grab,maurobaraldi/grab,shaunstanislaus/grab,SpaceAppsXploration/grab,codevlabs/grab,pombredanne/grab-1,codevlabs/grab,lorien/grab,istinspring/grab,giserh/grab,DDShadoww/grab,alihalabyah/grab,istinspring/grab,giserh/grab,SpaceAppsXploration/grab,pombredanne/grab-1,huiyi1990/grab,DDShadoww/grab,maurobaraldi/grab,liorvh/grab,lorien/grab