added Google+ and Twitter social buttons

I added Google+ and Twitter social buttons on post metadata line. I guess this will help spreading word a bit.

I also added some css hacks preventing embedded buttons to take some extra width they won't use so they look close to each other now.

---------

![screen shot 2013-10-31 at 11 48 08 am](https://f.cloud.github.com/assets/159209/1448811/028e0036-425d-11e3-9db3-4d4aa809ed2e.png)