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

appveyor.yml

@@ -50,8 +50,7 @@ test_script:
 
 before_deploy:
   # Generate artifacts for release
-  # TODO(burntsushi): How can we enable SSSE3 on Windows?
-  - cargo build --release
+  - cargo build --release --features unstable
   - mkdir staging
   - copy target\release\rg.exe staging
   - ps: copy target\release\build\ripgrep-*\out\_rg.ps1 staging