README.md: Bump min Rust version to 1.31+
tmkms now requires the 2018 edition of Rust
@@ -66,7 +66,7 @@ prerequisites for support.
You will need the following prerequisites:
-- **Rust** (stable; 1.27+): https://rustup.rs/
+- **Rust** (stable; 1.31+): https://rustup.rs/
- **C compiler**: e.g. gcc, clang
- **pkg-config**
- **libusb** (1.0+). Install instructions for common platforms:
