Bump md5 version

The changelog only consists of:
>     Update to digest v0.10 (#217)

So this one should be pretty safe

Signed-off-by: Jonathan Schwender <[email protected]>

Author: jschwe

Cargo.lock

@@ -51,7 +51,7 @@ libc = "0.2.10"
 linked-hash-map = "0.5"
 local-encoding = "0.2.0"
 log = "0.4"
-md-5 = { version = "0.9", optional = true }
+md-5 = { version = "0.10.0", optional = true }
 memcached-rs = { version = "0.4" , optional = true }
 num_cpus = "1.0"
 number_prefix = "0.4"