bump MSRV to 1.40

Author: ZuseZ4

.travis.yml

@@ -4,7 +4,7 @@ sudo: required
 dist: trusty
 matrix:
   include:
-    - rust: 1.37.0
+    - rust: 1.40.0
       env:
        - FEATURES='test docs'
        - RUSTFLAGS='-D warnings'

src/lib.rs

@@ -61,7 +61,7 @@
 //!     needs matching memory layout to be efficient (with some exceptions).
 //!   + Efficient floating point matrix multiplication even for very large
 //!     matrices; can optionally use BLAS to improve it further.
-//! - **Requires Rust 1.37 or later**
+//! - **Requires Rust 1.40 or later**
 //!
 //! ## Crate Feature Flags
 //!