timestamps each log entry

So, here it is.

I ran "rake tests", and one test failed, but it has something to do with locking, so I don't think I broke anything:

```
  1) bitpocket locking exits with status 1 when other instance is running
     Failure/Error: sync.should exit_with(1)
       expected 2 to exit with 1
     # /home/lucastx/src/bitpocket/spec/locking_spec.rb:9:in `block (2 levels) in <top (required)>'
```