changes "free" to "paid" for holidayapi.com since its not free anymore

README.md

@@ -102,7 +102,7 @@ Please note a passing build status indicates all listed APIs are available since
 | API | Description | Auth | HTTPS | Link |
 |---|---|---|---|---|
 | Church Calendar | Catholic liturgical calendar | No | No | [Go!](http://calapi.inadiutorium.cz/) |
-| Holidays | Free API for obtaining information about holidays. | `apiKey` | Yes | [Go!](https://holidayapi.com/) |
+| Holidays | *PAID* API for obtaining information about holidays. | `apiKey` | Yes | [Go!](https://holidayapi.com/) |
 | LectServe | Protestant liturgical calendar | No | No | [Go!](http://www.lectserve.com) |
 | Non-Working Days | Database of ICS files for non working days | No | Yes | [Go!](https://github.com/gadael/icsdb) |