Revert "removed unsafe code in favor of explicit assert"

This reverts commit 479d756c99.

There’s nothing wrong with this patch, but I had never pulled this
commit to my local repository and had completely forgotten about it, and
today removed the unsafe code in a *different* direction that I like
better (`bytes.try_into().map(|bytes| u64::from_ne_bytes(bytes))`), so
reverting it so I can cleanly rebase is just easier for me!

src/raw.rs

@@ -10,6 +10,7 @@ use std::hash::{Hasher, BuildHasherDefault};
 #[cfg(test)]
 use std::mem;
 use std::ops::{Index, IndexMut};
+use std::ptr;
 
 use any::{Any, UncheckedAnyExt};
 
@@ -22,11 +23,10 @@ impl Hasher for TypeIdHasher {
     #[inline]
     fn write(&mut self, bytes: &[u8]) {
         // This expects to receive one and exactly one 64-bit value
-        assert!(bytes.len() == 8);
-        self.value = u64::from(bytes[0])       | u64::from(bytes[1]) << 8  |
-                     u64::from(bytes[2]) << 16 | u64::from(bytes[3]) << 24 |
-                     u64::from(bytes[4]) << 32 | u64::from(bytes[5]) << 40 |
-                     u64::from(bytes[6]) << 48 | u64::from(bytes[7]) << 56;
+        debug_assert!(bytes.len() == 8);
+        unsafe {
+            ptr::copy_nonoverlapping(&bytes[0] as *const u8 as *const u64, &mut self.value, 1)
+        }
     }
 
     #[inline]