run gofmt
remove extra copy(?)

Unsure if this actually copies it, but it seemed pretty unnecessary.
Use local RNG

When you use the top-level functions, you have to wait for mutexes,
since it's written to be threadsafe. To avoid that overhead, you can
instantiate your own RNG. This amounted to 13% speedup on my system.
Merge pull request #2 from treed/master

Some go fixes