grok Pattern in file, should trim ending spaces

[woodyyou]

I put grok patterns in a file, didn't realized there was a space at the end. It resulted not match. Took me quite some time to figure out that's the problem (need to use rubydebug to tell there's a parsing error, even -v didn't tell).

Since leading spaces do not matter, ending space should not either. Also, I think it's a common mistake.

[jordansissel]

Fair point. +1.

Related, could be lovely if Grok would offer a nicer way to automate debugging of where in a pattern it didn't match.

[talevy]

PR for rejecting patterns with trailing whitespaces: jordansissel/ruby-grok#15

[jordansissel]

For Logstash 1.5.0, we've moved all plugins to individual repositories, so I have moved this issue to logstash-plugins/logstash-filter-grok#36. Let's continue the discussion there! :)