Support for SIMD operations for RGG1555

Description

Up to 3x the performance for RGG1555 with SIMD operations. The current implementation is hardcoded for 16 bytes at a time (128 bits). Still requires some testing and validation for AVX2 and AVX512.

Fixes #45 (closed)

.gitlab-ci.yml

@@ -78,7 +78,8 @@ test-rust:
     - rustup override set $RUST_VERSION
     - rustc --version
     - cargo test
-    - cargo bench --features simd
+    - if [[ $RUST_VERSION != nightly ]]; then cargo bench; fi
+    - if [[ $RUST_VERSION == nightly ]]; then cargo bench --features simd; fi
 
 test-pyo3:
   stage: test