MAINT: Require Rust 1.24 as minimum version

Author: bluss

.travis.yml

@@ -2,7 +2,7 @@ language: rust
 sudo: false
 matrix:
   include:
-    - rust: 1.22.0
+    - rust: 1.24.0
     - rust: stable
     - rust: beta
     - rust: nightly

src/lib.rs

@@ -42,7 +42,7 @@
 //!
 //! ## Rust Version
 //!
-//! This version of itertools requires Rust 1.12 or later.
+//! This version of itertools requires Rust 1.24 or later.
 //!
 //! [`Iterator`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html
 #![doc(html_root_url="https://docs.rs/itertools/0.7/")]