Always test libm support

Author: cuviper

README.md

@@ -29,7 +29,6 @@ default-features = false
 ```
 
 The `Float` and `Real` traits are only available when either `std` or `libm` is enabled.  
-The `libm` feature is only available with Rust 1.31 and later ([see PR #99](https://github.com/rust-num/num-traits/pull/99)).
 
 The `FloatCore` trait is always available.  `MulAdd` and `MulAddAssign` for `f32`
 and `f64` also require `std` or `libm`, as do implementations of signed and floating-

ci/test_full.sh

@@ -27,8 +27,7 @@ if ! check_version $MSRV ; then
   exit 1
 fi
 
-FEATURES=()
-check_version 1.27 && FEATURES+=(libm)
+FEATURES=(libm)
 echo "Testing supported features: ${FEATURES[*]}"
 
 set -x