Allow V8 to optimize the logging functions by not leaking the arguments object
and reduce the number of object accesses in the toLevel function.
This results in a performance improvement of about 11%.
Updated logger.js to support disabling all log writes.
Updated log4js.js shutdown function to disable log writes.
Added tests.
Update gitignore to ignore rolling date stream's test output.
using levels.toLevel and this.isLevelEnabled prior to emiting the event will prevent the appenders from being notified if the log level provided is below the loggers level.