Change source URL for certdata.txt to HTTPS

Fix jublo#149.

Author: mynetx

src/cacert.pem

@@ -6,7 +6,7 @@
 ## This is a bundle of X.509 certificates of public Certificate Authorities
 ## (CA). These were automatically extracted from Mozilla's root certificates
 ## file (certdata.txt).  This file can be found in the mozilla source tree:
-## http://hg.mozilla.org/releases/mozilla-release/raw-file/default/security/nss/lib/ckfw/builtins/certdata.txt
+## https://hg.mozilla.org/releases/mozilla-release/raw-file/default/security/nss/lib/ckfw/builtins/certdata.txt
 ##
 ## It contains the certificates in PEM format and therefore
 ## can be directly used with curl / libcurl / php_curl, or with