Change base_uri to use HTTPS instead of HTTP

Pipedrive will deprecate HTTP API access on May 11, 2015.

Author: martintajur

lib/pipedrive/base.rb

@@ -16,7 +16,7 @@ class Base < OpenStruct
 
     include HTTParty
 
-    base_uri 'api.pipedrive.com/v1'
+    base_uri 'https://api.pipedrive.com/v1'
     headers HEADERS
     format :json