Grok does create field when pattern matches all message

As of today grok filter does not create a specific field
if the grok matches the whole message. This commit changes
this behavior and make grok create the required field in
the configuration file
add alternative tags on grokparsefailure
enhanced translate filter
some doc updates and typo fixes
blocking congestion check implementation for redis output
fix typo
don't check for congestion on teardown
debug msg when trying to split a non-string type
Merge pull request #421 from cosmok/mutate_add_debug

debug msg when trying to split a non-string type
LOGSTASH-978 - an input for the varnish shared memory binary log
Added minor addition about how to invoke gems installed in ruby gembag.rb logstash.gemspec into an irb session
Updated based on @jordansissel input
Fixed typo
Added HipChat output.
- Add a sleep filter
- Use Stud::Task to more easily manage any exceptions from the Agent
runner
- Add experimental ruby filter
- Add example parsing the graphite carbon text protocol
- exit nonzero on configuration errors; this also has the intentional
effect of not barfing a stack trace on config errors.
- improve validation reporting
- check to_f and to_i conversions with :number validation