AddVersionCommand adds the version command via Cobra.

CheckExecutableVersion will attempt to show the version of the executable and if shown, will immediately exit.

GetVersion returns the executable version as a string.

SetDefaultGlogStderr will prevent the glog package from defaulting to creating new log files on every execution, set the logtostderr option for glog to true if it wasn't specified on the command line.

SetFlagIfNotProvided sets a command line flag if it wasn't provided.

ShowVersion checks for "version" to be the only argument and if true, writes the version to the io.Writer passed in.