Use a familiar way to specify compiler versions
diff --git a/src/lib.rs b/src/lib.rs
index 5953c64..4e45405 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -103,7 +103,7 @@
//! ```
//!
//! The [`heapsize`] example directory shows a complete working Macros 1.1
-//! implementation of a custom derive. It works on any Rust compiler \>=1.15.0.
+//! implementation of a custom derive. It works on any Rust compiler 1.15+.
//! The example derives a `HeapSize` trait which computes an estimate of the
//! amount of heap memory owned by a value.
//!