adds style/overview.md back in

[mosesn]

motivation

This page is linked to by http://docs.scala-lang.org/style/ and http://davetron5000.github.com/scala-style/ so even if this is supposed to be destroyed, it should at least be replaced with a permanent redirect instead of a file not found.

different behavior

Just a reversion back to the style/overview.md of 59afeb1. I think the breaking commit was 8abc6d1.

[heathermiller]

Thanks for your pull, but the removal of this page was actually intended. The fact that there was a broken link there, though, was not- thanks a lot for catching it! The overview page was migrated from elsewhere and was a bit more eccentric than any of us initially realized (accidentally overlooked). Instead, I simply added a different overview page back where it used to be. Thanks again for catching this!