More control over select clause

Should close #374.

Should resolve half of #374.

Add street accessors to Google result

Patch to fix issue #369.  Handles comma separated values for HTTP_X_FORWARDED_FOR header

Fix syntax error in initializer.rb template.

MapQuest doesn't require a key for the "open" API, but the
geocoder throws an error if you don't provide one anyway.
This edit makes the API key optional.

No longer do we install libs as plugins.

Now it is necessary to specify which service is being used:
  Geocoder.configure(:maxmind => {:service => ...})
where '...' is one of: < :country | :city | :city_isp_org | :omni >

If you do this:

  Geocoder::Query.new("Kremlin, Moscow", :params => {:language => "ru"})

you should get a response in Russian ("ru") regardless of the value set
in Geocoder.configure(...).

Either do it consistently across Ruby versions, or don't do it at all.
Plus, it didn't seem to work.