Add CI on stable 1.42
diff --git a/src/lib.rs b/src/lib.rs
index 24c5eaf..48c3b72 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,8 +10,7 @@
 //!
 //! <br>
 //!
-//! *Compiler support: requires rustc 1.42+ (beta on January 30, stable on March
-//! 12)*
+//! *Compiler support: requires rustc 1.42+*
 //!
 //! <br>
 //!