docs(readme): updated contact links

Fixed Discord link and removed outdated Gitter link.

Closes #77.

Author: arctic-hen7

README.md

@@ -76,7 +76,7 @@ These tasks will be done after Perseus is stable.
 
 We appreciate all kinds of contributions, check out our [contributing guidelines](./CONTRIBUTING.md) for more information! Also, please be sure to follow our [code of conduct](./CODE_OF_CONDUCT.md).
 
-You can also chat about Perseus at our [Gitter link](https://gitter.im/perseus-framework/community), or (for Sycamore-related stuff) on [our channel on Sycamore's Discord server](https://discord.com/channels/820400041332179004/883168134331256892).
+You can also chat about Perseus on [our channel on Sycamore's Discord server](https://discord.com/channels/820400041332179004/883168134331256892).
 
 ## License