Update mcmod.info

"authors" is deprecated. It's "authorList" now.
And why don't you add your logo? Just copy your "steamcraftlogoblank.png" file in the resources folder and name it "steamcraft.png".
I think I can not upload files to your project, but I tried the logo locally on my machine and it looks perfect in the mod overview.
Merge pull request #77 from Gholuk/patch-4

Update mcmod.info