Add reflection check for Spring 4.1 in Mail Writer tests

As part of the Spring Framework 4.1 updates, the send methods on both
MailSender#send and JavaMailSender#send were converted from taking an
array to vargs.  This commit adds a reflection check to determine which
version of Spring it's being built against and uses the apropriate
mocking checks in these tests based on that check.
Changed repository references from http to https