Resolve build deprecation warning

* Resolve build warning: Deprecation: `std.net.curl.dur` is not visible
from module by adding std.datetime & reordering dependancy import order

src/util.d

@@ -1,8 +1,9 @@
 import std.base64;
 import std.conv;
 import std.digest.crc, std.digest.sha;
-import std.file;
 import std.net.curl;
+import std.datetime;
+import std.file;
 import std.path;
 import std.regex;
 import std.socket;