BUG When loading patterns files.

[visaxin]

I think we should add a specific Filename Extension for pattern files.

• Version:
• Operating System: Ubuntu 14.0
• Config File (if you have sensitive info, please remove it):
• Sample Data:
• Steps to Reproduce: add a folder contains NO PATTERN files under [logstashDIR]/vendor/bundle/jruby/1.9/gems/logstash-patterns-core-2.0.5/patterns/

NO PATTERN files eg:[logstashDIR]/vendor/bundle/jruby/1.9/gems/logstash-patterns-core-2.0.5/patterns/_md5/_message.md5

cat _message.md5 d41d8cd98f00b204e9800998ecf8427e