MAINT: Increase MSRV to 1.49

1.49 had a lot of fixes to associated types and bounds, and that enables
the new DataOwned changes to compile.

Author: bluss

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           - stable
           - beta
           - nightly
-          - 1.42.0  # MSRV
+          - 1.49.0  # MSRV
 
     steps:
       - uses: actions/checkout@v2

src/lib.rs

@@ -62,7 +62,7 @@
 //!     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 1.42 or later**
+//! - **Requires Rust 1.49 or later**
 //!
 //! ## Crate Feature Flags
 //!