Added support for setting transport flags (No check SSL cert) to git_clo...

As issue #1147, I was unable to git_clone a repository from github that used https, because it complained that the SSL certificate is invalid, so I added an option to git_clone to set the transport flags that will be used during the clone.

More specifically, it checks to see if the transport flags == `GIT_TRANSPORTFLAGS_NO_CHECK_CERT` and if so it calls `git_remote_check_cert(origin, 0))` to set the correct options.