Extract url to object

Extracts the `Entity::url` method out into a `SecQuery::SecURI` object that can be used to build up urls for accessing common endpoints. This will shorten the Entity class and create a place to store logic for other endpoints. 

Currently there are two main public class methods for building urls:
```rb
SecURI.browse_edgar_uri( query_string_options or string ) # will build with /browse-edgar/
SecURI.ownership_display_uri( query_string_options or string ) # will build with /own-disp/
```

Uses `Addressable::URI` for building up resulting string for url.

+ fixed some more rubocops in the gemspec file.
+ alphabetized includes in sql_query.rb
+ added specs for public methods of sec_uri