Add the most common Apache log formats available as class constants

[weppos]

Add the most common Apache log formats available as class constants. For instance, the user might want to do

parser = ApacheLogRegex.new(ApacheLogRegex::COMBINED_LOG_FORMAT)

or

parser = ApacheLogRegex.new(:combined)

via http://www.simonecarletti.com/blog/2009/02/apache-log-regex-a-lightweight-ruby-apache-log-parser/

[dcolebatch]

Yes please, that would be awesome!