added example and docs for secure image over https

started using this parameter in my code. thought it should be added to
the docs.

Author: schallereqo

EXAMPLES.md

@@ -98,6 +98,8 @@ client.connections
 ```
 # get the original picture-url for one of the connections
 client.picture_urls(:id => 'id_of_connection')
+# get the image over https instead of http
+client.picture_urls(:id => 'id_of_connection', :secure => "true")
 
 ## Update User's Status
 

lib/linked_in/api/people.rb

@@ -60,6 +60,7 @@ def new_connections(modified_since, options={})
       #
       # @options [String] :id, the id of the person for whom you want the profile picture
       # @options [String] :picture_size, default: 'original'
+      # @options [String] :secure, default: 'false', options: ['false','true']
       #
       # example for use in code: client.picture_urls(:id => 'id_of_connection')
       def picture_urls(options={})