bootstrap

This change is a follow up to the bootstrap discussion.


@spencerkimball This is building cockroach, not rocksdb. 

@strangemonad If someone doesn't want to hack, they should be getting a binary distribution. I imagine you'll want to make right after running bootstrap, but I wouldn't want anyone to get confused that they should be running bootstrap in order to build cockroach. The standard workflow should be run bootstrap every once in a while and run make frequently.