Add categories to Cargo.toml
diff --git a/Cargo.toml b/Cargo.toml
index b4320d0..755b6f1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,7 @@
 Random number generators and other randomness functionality.
 """
 keywords = ["random", "rng"]
+categories = ["algorithms"]
 
 [dependencies]
 libc = "0.2"