avoid logging in the library, and avoid using glog

[aybabtme]

The library pulls in github.com/golang/glog for logging. That package installs global flags in the stdlib flag package, which means applications using embd get a bunch of flags pulled in by default, which is a bit unsightly.

For instance, I declared 3 flags for my app:

var (
    pinID     = flag.Int("pin", 10, "pin to use")
    direction = flag.String("direction", "in", "in|out")
    format    = flag.String("format", "hex", "hex|bin")
)
flag.Parse()

...yet glog, thru embd, pollutes my command with a bunch of flags.

$ uartdump -h
Usage of uartdump:
  -alsologtostderr
        log to standard error as well as files
  -direction string
        in|out (default "in")
  -format string
        hex|bin (default "hex")
  -log_backtrace_at value
        when logging hits line file:N, emit a stack trace
  -log_dir string
        If non-empty, write log files in this directory
  -logtostderr
        log to standard error instead of files
  -pin int
        pin to use (default 10)
  -stderrthreshold value
        logs at or above this threshold go to stderr
  -v value
        log level for V logs
  -vmodule value
        comma-separated list of pattern=N settings for file-filtered logging

Note that in general, it's a bit of an anti-pattern for libraries to log. There's some cases where it makes sense tho, and in those case libraries should avoid linking against a specific implementation and instead take an injectable interface.

I've seen only 1 such usage of glog and it feels to me that it isn't necessary. If my argument makes sense to you, I'm happy to send a PR.