Require CMake version 2.8.12 or later.
Require CMake version 2.8.12 or later.

Fixes #110.

Change-Id: I64b92c56fd8b08365a0b1e9b64aa6410467eee1a
Reviewed-on: https://code-review.googlesource.com/7154
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2