Avoid logging mulitple times for performance gains.

Before: 
![screenshot from 2014-07-07 09 29 06](https://cloud.githubusercontent.com/assets/4335742/3490656/21041f8c-0576-11e4-8c75-83929fb09767.png)

After: 
![screenshot from 2014-07-07 09 29 12](https://cloud.githubusercontent.com/assets/4335742/3490657/2148180e-0576-11e4-9847-19daaa1b5850.png)

@tgxworld I don't find a reason in the linked docs why you should not end up with:

```ruby
irb(main):001:0> require "logger"
=> true
irb(main):002:0> l = Logger.new(STDOUT)
=> #<Logger:0x007f9a7912a320 @progname=nil, @level=0, @default_formatter=#<Logger::Formatter:0x007f9a7912a2f8 @datetime_format=nil>, @formatter=nil, @logdev=#<Logger::LogDevice:0x007f9a7912a2a8 @shift_size=nil, @shift_age=nil, @filename=nil, @dev=#<IO:<STDOUT>>, @mutex=#<Logger::LogDevice::LogDeviceMutex:0x007f9a7912a280 @mon_owner=nil, @mon_count=0, @mon_mutex=#<Mutex:0x007f9a7912a230>>>>
irb(main):004:0> l.info "1"; l.info "2"; l.info "3"; nil
I, [2014-07-16T15:47:10.250089 #28591]  INFO -- : 1
I, [2014-07-16T15:47:10.250200 #28591]  INFO -- : 2
I, [2014-07-16T15:47:10.250235 #28591]  INFO -- : 3
=> nil
irb(main):005:0> l.info "1\n2\n3"; nil
I, [2014-07-16T15:47:20.169488 #28591]  INFO -- : 1
2
3
=> nil
```