point to Slack not Gitter

README.md

@@ -46,10 +46,7 @@ Greener JG, Selvaraj J and Ward BJ. BioStructures.jl: read, write and manipulate
 We appreciate contributions from users including reporting bugs, fixing issues,
 improving performance and adding new features.
 
-Detailed guidance for contributing to all BioJulia packages is provided at the
-[BioJulia Contribution Documentation](https://github.com/BioJulia/BioStructures.jl/blob/master/CONTRIBUTING.md).
-
 If you have a question about contributing or using this package, you are
 encouraged to use the
-[BioJulia Gitter](https://gitter.im/BioJulia/General) or the
+#biology channel of the [Julia Slack](https://join.slack.com/t/julialang/shared_invite/zt-1ab2rnvlw-mfODD9DJC_apVEULyKXDrA) or the
 [Bio category of the Julia discourse site](https://discourse.julialang.org/c/domain/bio).