Include CMakeLists.txt into tarball

Change-Id: I1901182bd1a4ed975e116316775f213f48e715a4
Reviewed-on: http://review.couchbase.org/27536
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>