basic BenchmarkMock()

cbugg: bug-788

To try it, use...

    go test -test.bench .

You should see output like...

    $ go test -test.bench .
    testing: warning: no tests to run
    PASS
    BenchmarkMock   2013/07/30 15:56:17 tuqtng started...
    2013/07/30 15:56:17 version: TEST
    2013/07/30 15:56:17 site: mock:items=10000
    2013/07/30 15:56:17 tuqtng started...
    2013/07/30 15:56:17 version: TEST
    2013/07/30 15:56:17 site: mock:items=10000
          20     70757779 ns/op
    ok    github.com/couchbaselabs/tuqtng   1.528s