Fix a few typos and make docs a bit more readable.
Begin converting literal named captures to Grok expressions.
Finished removing literal named captures from Cisco ASA Grok patterns
Fix SINCEDB_DIR environment variable name
[oldlogstashjson] add tests before making changes
[oldlogstashjson] encode to json instead of ruby hash (LOGSTASH-1626)
[oldlogstashjson] fix test assertions

Still do not fully grok the insist blocks or rspec testing,
but at least we're really making assertions now.
Add metric_type as part of the validation strings included in the plugin.
Merge branch 'master' into fix-datadog-validation
[oldlogstashjson] less convoluted not nil assertions
[imap] decode header values in RFC 2047 encoded-word format

RFC 2047 outlines an encoding for header fields.  Without this
change the header fields (To, From, Subject, etc.) may have
values like `=?iso-8859-1?Q?abc?=` instead of `abc`.
[LOGSTASH-1630] Syslog 5424 patterns fail to match additional spaces

https://logstash.jira.com/browse/LOGSTASH-1630

Split the start of `SYSLOG5424LINE` out to `SYSLOG5424BASE`, in case
people want to create PAM or CRON patterns, similar to those available
for `SYSLOG`.

Also make syslog5424_sd optionally match nothing, since it seems to be
ommitted entirely with rsyslog's `RSYSLOG_SyslogProtocol23Format` (ie -
there is no SD data, and it is not correctly replaced with a `-`).
Merge pull request #791 from pdf/LOGSTASH-1630

[LOGSTASH-1630] Syslog 5424 patterns fail to match additional spaces
Merge pull request #790 from bfritz/imap-decode-header-values

[imap] decode header values in RFC 2047 encoded-word format
Merge pull request #789 from cparedes/fix-datadog-validation

Fix datadog validation
Merge pull request #788 from bfritz/LOGSTASH-1626-fix-oldlogstashjson-codec

LOGSTASH-1626 - encode to JSON instead of ruby hash
Merge pull request #774 from davialexandre/patch-1

Fix SINCEDB_DIR environment variable name
fix regressions in input/gelf

- fixed regression that caused 'gelf listener died' on chunked messages
- moved client ip of the sender from `event['host']` to `event['source_host']` since this will overwrite the (probably hostname) in the GELF message with an IP address. The hostname is thus lost and would require resolving in a logstash filter or by modifying upstream GELF clients. This is sort of a regression in that previous versions of logstash would leave the `host` field alone and use the client[3] ip as part of the `@source_host`.
- previous versions did not remove the leading `_` from keys. In order to smooth the upgrade process, make this optional
with new `strip_leading_underscore` (boolean) config attribute. It's useful to keep this separate from `remap` since this
 restores previous behavior.
- Remove link to releases that no longer exists.
Merge pull request #794 from logstash/remove-releases-list

- Remove link to releases that no longer exists.