* .gitignore, pollen.go, pollen_test.go:
  - This changes the 'handler' from being just a func() using global
    state to being a struct with local state.
  - It then moves the things like dev and log to being members of the
    struct, with interfaces that let us override them in the test suite.
  - It then adds a bunch of tests about how we handle failures, errors,
    logging, the size flag, etc.
  - The interfaces also mean that we won't try to spam syslog while running
    the test suite.
  - Another small change is that if you do:
       pollen -https-port=""
    Then it won't try to bind to the HTTP port with a cert.
  - Since I'm not the official source for pollen, it helped for testing at
    least the HTTP requests manually.
  - This also fixes the help text for "-size" since it doesn't actually
    change how much content we send on the wire, but how much content we
    read from /dev/urandom (but it adds tests for that fact).