Skip missing fields, as converting those introduces new fields.
Explicitly specify fields to be ignored for GELF.
Add parameter to select the field that provides the GELF short message.
Fix spacing.
- use the client's address for the source host of the event instead of
  the listen address of the server. (LOGSTASH-796)
- fill in changelog from git log review up to commit
f974bb4f680eab0bfb4d9a470dad4a0c65436380 (Jan 2 11:10:43 2013 -0800)
Fixed some code blocks issues in kv and date filters docs
Merge pull request #300 from jamtur01/codeblocksfix

Fixed some code blocks issues in kv and date filters docs
Fix class discovery for Threadables
- try to clarify 'one of these things'
- deprecate the config /..../ regexp crap from date
Deprecate the regexp config crap
Deprecate regexp match shorthand for grok
Try to improve the docs for xml
Add more examples and doc improvements
- make common settings like filter 'remove_tag' use the literal plugin
  name instead of the text "myfilter" in examples.
fix one more instance of 'myfilter' -> %PLUGIN%
- link to joda's docs
- only do string conversion on symbols (config :some_symbol).
  This keeps support for regexp configs until I finally remove that.
- link to releases hosted on dreamobjects
- clean up intro on simple getting started