Merge remote-tracking branch 'origin/master'

Author: Alexandr Shurigin

README.markdown

@@ -14,6 +14,7 @@ year - \d{4}
 month - (0?([1-9])|10|11|12)
 day - ((0|1|2)?([1-9])|[1-3]0|31)
 id - \d+
+pk - \d+
 uuid - [a-fA-F0-9]{8}-?[a-fA-F0-9]{4}-?[a-fA-F0-9]{4}-?[a-fA-F0-9]{4}-?[a-fA-F0-9]{12}
 ```