only create factory once

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
allow speicfying a SslContext

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
bump to 1.5

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>