Fix whitespace

Author: mhluska

lib/blockcypher/api.rb

@@ -267,7 +267,7 @@ def event_webhook_subscribe(url, event, options = {})
 
       api_http_post('/hooks', json_payload: payload)
     end
-	  
+
     def event_webhook_listall
       api_http_get('/hooks')
     end