Removing 2.6 and 2.5-dev from travis-ci build.
Removing 2.6 and 2.5-dev from travis-ci build.

jentjr/flopy,jentjr/flopy,brclark-usgs/flopy,aleaf/flopy,aleaf/flopy,bdestombe/flopy-1,brclark-usgs/flopy,mrustl/flopy