remove example extension for OFN initializer; use file expand in seeds.rb instead of require_relative

Two minor changes:
1) I needed to remove the ".example" extension from the file config\initializers\open_food_network.rb.example  file. (I'm sure that just didn't get committed into the branch as you wanted to)
2) in seeds.rb, I changed the way the path to suburb_seeds.rb is called:  it did use a <code>require_relative</code> , but that wouldn't work when I used my debugger (RubyMine). [probably because seedBank was doing a code_eval, and that was being called from a rake task, *and* it was being run with the debugger, so the original path wasn't quite what it used to be (pre-seedBank).]
 I changed it to <code>File.expand(.....,__FILE__)</code>.

Both of those are super minor (and (2) will become moot soon). I thought I'd do a pull request since I hadn't talked to you beforehand about changing anything.  And I wanted to practice uploading and doing a pull request.  (Which apparently I needed, since I first pushed this to the OFN repo! <sigh>)

You can hold off on pulling these since they're minor and might be moot.  Or you can make these same changes in your commits as you do the seedBank work. Doesn't matter on my end.