Eliminate deprecation warning re use_bin_type

When 'use_bin_type' option is not set explicitly, msgpack-0.5.0 (and
only it, not 0.5.1 or newer) warns a user that its default value will be
changed in a future.

The main reason of the change is to allow
test_03_discovery_bad_good_addresses() test from test_mesh.py to pass on
msgpack-0.5.0: it counts deprecation warnings produced by a call and so
affected if unexpected warnings are emitted.

This commit is prerequisite to enable msgpack-0.5.0 in CI, which is done
in the next commit.

Follows up #155

Author: Totktonada

tarantool/request.py

@@ -74,8 +74,19 @@ def __init__(self, conn):
         #
         # The default behaviour of the connector is to pack both
         # bytes and Unicode strings as mp_str.
-        if msgpack.version >= (1, 0, 0):
-            packer_kwargs['use_bin_type'] = False
+        #
+        # msgpack-0.5.0 (and only this version) warns when the
+        # option is unset:
+        #
+        #  | FutureWarning: use_bin_type option is not specified.
+        #  | Default value of the option will be changed in future
+        #  | version.
+        #
+        # The option is supported since msgpack-0.4.0, so we can
+        # just always set it for all msgpack versions to get rid
+        # of the warning on msgpack-0.5.0 and to keep our
+        # behaviour on msgpack-1.0.0.
+        packer_kwargs['use_bin_type'] = False
 
         self.packer = msgpack.Packer(**packer_kwargs)