Fix https:// notifications if TLSvX is mandatory

Nowadays servers tend to use TLSv1.[12] and SSLv3 will start to disappear
as only ie6 requires it…
In the post-receive hook SSLv3 is forced and notification fails
if server only accepts TLSv1.[12]
(eg: server gets 'A+' on https://www.ssllabs.com/ssltest/)

```
remote: Notifying Redmine about changes to this repository : 'project/repo' ...
remote: Redmine URL : 'https://myforge/githooks/post-receive/redmine/project'
remote: HTTP_ERROR : SSL_connect returned=1 errno=0 state=SSLv3 read server hello A: sslv3 alert handshake failure
remote: Error contacting Redmine about changes to this repo.
```

This change let ruby's ssl stack negociate protocol with the server (works for me™ with a TLS-only server)
default seems to negociate SSL/TLS protocol