Feature/add logstash directory in rspec

Feel free to delete it, it was a test after messing with my vimscripts..

I was wondering why we did not have a logstash folder inside the spec folder.
There is a lot of editing tools or plugins (ruby.vim, textmate ruby) that
allow easy navigation to the alternate version of the current file (code file vs spec file)
if both directories have the same structure and naming convention.

Also I am it remove the need of the core directory. 
while changing this, we should use Environment#pattern_path