File path filtering works and is pretty fast.

I'm pretty disappointed by the performance of regex sets. They are
apparently spending a lot of their time in construction of the DFA,
which probably means that the DFA is just too big.

It turns out that it's actually faster to build an *additional* normal
regex with the alternation of every glob and use it as a first-pass
filter over every file path. If there's a match, only then do we try the
more expensive RegexSet.

Cargo.toml

@@ -29,6 +29,9 @@ regex-syntax = { version = "0.3.1", path = "/home/andrew/rust/regex/regex-syntax
 rustc-serialize = "0.3"
 walkdir = "0.1"
 
+[features]
+simd-accel = ["regex/simd-accel"]
+
 [dev-dependencies]
 glob = "0.2"
 lazy_static = "0.2"