Revert Travis checks for Python version 2.4-2.6
Revert Travis checks for Python version 2.4-2.6

We don't try to run the test suite for python version 2.4, 2.5 or 2.6 as
the test suite relies on functionality introduced in 2.7.

SoundGoof/NIPAP,fredsod/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,bbaja42/NIPAP,plajjan/NIPAP,SpriteLink/NIPAP,fredsod/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,fredsod/NIPAP,ettrig/NIPAP,SoundGoof/NIPAP,SoundGoof/NIPAP,garberg/NIPAP,plajjan/NIPAP,bbaja42/NIPAP,plajjan/NIPAP,SpriteLink/NIPAP,plajjan/NIPAP,fredsod/NIPAP,ettrig/NIPAP,garberg/NIPAP,garberg/NIPAP,ettrig/NIPAP,ettrig/NIPAP,garberg/NIPAP,fredsod/NIPAP,bbaja42/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,fredsod/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,SpriteLink/NIPAP,SoundGoof/NIPAP,SpriteLink/NIPAP,plajjan/NIPAP,SoundGoof/NIPAP,plajjan/NIPAP