Merge pull request #208 from mat128/slack

Add Slack to README

README.md

@@ -23,6 +23,7 @@ conditions.  ZNC Push current supports the following services:
 * [Pushalot][]
 * [Pushjet][]
 * [Telegram][]
+* [Slack][]
 * Custom URL GET requests
 
 This project is still a Work In Progress, but should be functional enough and stable enough
@@ -249,6 +250,7 @@ to something similar to "http://domain/#channel/2011-03-09 14:25:09", or
     *   `nexmo`
     *   `pushjet`
     *   `telegram`
+    *   `slack`
     *   `url`
 
 *   `username` Default: ` `
@@ -534,6 +536,7 @@ from me and not from my employer.  See the `LICENSE` file for details.
 [Pushalot]: https://pushalot.com/
 [Pushjet]: http://pushjet.io
 [Telegram]: https://telegram.org/
+[Slack]: https://slack.com/
 
 [faq]: https://github.com/jreese/znc-push/blob/master/doc/faq.md
 [examples]: https://github.com/jreese/znc-push/blob/master/doc/examples.md