Stream tests use `tarantool -V` output to check version. For Tarantool
Enterprise, `tarantool -V` output is "Tarantool Enterprise <version>",
thus it is incorrect to extract the version tag by splitting by spaces.

Part of igorcoding#22

This patch adds support for using SSL to encrypt the client-server
communications [1]. The patch is based on a similar patch in
tarantool/tarantool-python connector [2].

To use SSL encrypted connection, use Connection parameters:

  conn = asynctnt.Connection(host='127.0.0.1',
                             port=3301,
                             transport=asynctnt.Transport.SSL,
                             ssl_key_file='./ssl/host.key',
                             ssl_cert_file='./ssl/host.crt',
                             ssl_ca_file='./ssl/ca.crt',
                             ssl_ciphers='ECDHE-RSA-AES256-GCM-SHA384')

If Tarantool server uses "ssl" transport, client connection also need to
use asynctnt.Transport.SSL transport. If server side had ssl_ca_file
set, ssl_key_file and ssl_cert_file are mandatory from the client side,
otherwise optional. CA file and ciphers are optional. See available
ciphers in Tarantool EE documentation [3].

1. https://www.tarantool.io/en/enterprise_doc/security/#enterprise-iproto-encryption
2. tarantool/tarantool-python#220
3. https://www.tarantool.io/en/enterprise_doc/security/#supported-ciphers

Closes igorcoding#22

SSL encrypted server could be started with Tarantool Enterprise 2.10 or
newer. To configure encryption, additional listen params must be passed.
ssl_key_file and ssl_cert_file are mandatory if transport is
asynctnt.Transport.SSL .

Follows up igorcoding#22

To run SSL tests, use Tarantool Enterprise 2.10 or newer and set
TEST_TT_SSL=TRUE flag. The patch is based on a similar patch in
tarantool/tarantool-python connector [1].

1. tarantool/tarantool-python#220

Follows up igorcoding#22