code: function getLevelStr (opts) {
    var lvlStr = _.invert(LEVELS)[opts.level]
      , useColours = opts.colourise || true;
  
    if (useColours) {
      switch (opts.level) {
        case LEVELS.DBG:
          lvlStr = colours.magenta(lvlStr);
          break;
        case LEVELS.INF:
          lvlStr = colours.green(lvlStr);
          break;
        case LEVELS.WRN:
          lvlStr = colours.yellow(lvlStr);
          break;
        case LEVELS.ERR:
          lvlStr = colours.red(lvlStr);
          break;
      }
    }
  
    return lvlStr;
  }
docs: Get the level string for a log, e.g "INF", "DBG" etc.
  Also adds colour to the when enabled.
  @param  {Object} opts