Set rust-version in Cargo.toml

Author: bluss

Cargo.toml

@@ -4,6 +4,7 @@ version = "0.7.4"
 authors = ["bluss"]
 license = "MIT OR Apache-2.0"
 edition = "2018"
+rust-version = "1.51"
 
 description = "A vector with fixed capacity, backed by an array (it can be stored on the stack too). Implements fixed capacity ArrayVec and ArrayString."
 documentation = "https://docs.rs/arrayvec/"