Wikitest

I have just extracted the wiki example from `cassandra_test.go` and put it in its own file. In addition, I have re-factored the code sightly and added a couple of benchmarks. The numbers are still quite high, but those can be addressed in further CLs.

    BenchmarkWikiCreateSchema            100         273775659 ns/op           11879 B/op         32 allocs/op
    BenchmarkWikiCreatePages           50000            657017 ns/op            6279 B/op         27 allocs/op
    BenchmarkWikiSelectAllPages         5000           3849620 ns/op           50838 B/op        388 allocs/op
    BenchmarkWikiSelectSinglePage     100000            221792 ns/op            7460 B/op         46 allocs/op
    BenchmarkWikiSelectPageCount       50000            723041 ns/op            5650 B/op         21 allocs/op

The usage of `testing.TB` will break the go1.1 build. I am in favor of dropping go1.1 support completely and adding go1.3 instead. Honestly, the Go team does a great job at keeping the API stable, therefore I can not think of a single reason for not using the latest (stable) version of Go. Supporting the latest two releases is probably fine.