Update the minimum Rust versino to 1.48.

Author: sunfishcode

README.md

@@ -22,7 +22,7 @@ if let Some((Width(w), Height(h))) = size {
 
 ## Minimum Rust Version
 
-This crate requires a minimum rust version of 1.31.0 (2018-12-06)
+This crate requires a minimum rust version of 1.48.0 (2020-11-19)
 
 ## License
 

src/lib.rs

@@ -2,7 +2,7 @@
 //!
 //! Supports both Linux, MacOS, and Windows.
 //!
-//!  This crate requires a minimum rust version of 1.31.0 (2018-12-06)
+//!  This crate requires a minimum rust version of 1.48.0 (2020-11-19)
 //!
 //! # Example
 //!