deps: update regex crate

This update brings with it a new feature of the regex crate which will
now use SIMD optimizations automatically at runtime with no necessary
compile time flags. All that's needed is to enable the `unstable` feature.

Other crates, such as bytecount and encoding_rs, are still using the
old-style SIMD support, so we leave the simd-accel and avx-accel features.
However, the binaries we distribute on Github no longer have those
features enabled, which makes them truly portable.

Fixes #135

1 files changed, 10 insertions, 1 deletions

diff --git a/README.md b/README.md
index c975791b..44e50eb3 100644
--- a/README.md
+++ b/README.md
@@ -286,6 +286,14 @@ If you're a **Rust programmer**, ripgrep can be installed with `cargo`.
 $ cargo install ripgrep
 ```
 
+If you're using Rust nightly, then use
+
+```
+$ cargo install ripgrep --features unstable
+```
+
+to get SIMD optimizations.
+
 ripgrep isn't currently in any other package repositories.
 [I'd like to change that](https://github.com/BurntSushi/ripgrep/issues/10).
 
@@ -312,7 +320,8 @@ RUSTFLAGS="-C target-cpu=native" cargo build --release --features 'simd-accel av
 ```
 
 If your machine doesn't support AVX instructions, then simply remove
-`avx-accel` from the features list. Similarly for SIMD.
+`avx-accel` from the features list. Similarly for SIMD (which corresponds
+roughly to SSE instructions).
 
 
 ### Running tests