Run tests only on node 4 and 0.10
Run tests only on node 4 and 0.10

iojs & 0.12 had no particulary wide spread, so I assume we can
drop them and test in node 4.x instead.

varya/gemini,HDevel/gemini,vladislav-sevostyanov/gemini,racing-post/gemini,HDevel/gemini,racing-post/gemini,pazone/gemini,pazone/gemini,gemini-testing/gemini,varya/gemini