Concurrent Adaptive Radix Tree

Simd+concurrent implementation of adaptive radix tree.

SIMD is using rust std's portable SIMD, which is currently only available on nightly, and adopts to any instruction sets that LLVM simd supports.

use concurrent_adaptive_radix_tree::ARTMap;

let mut map = ARTMap::new();
map.insert("foo", 1);
map.insert("bar", 2);
map.insert("baz", 3);
assert_eq!(map.len(), 3);

assert_eq!(map.get("foo"), Some(&1));
assert_eq!(map.get("bar"), Some(&2));
assert_eq!(map.get("baz"), Some(&3));