Add tds_version paramenter to pymssql.connet().

It has a default value of '7.1' to match the default value of the
underlying _mssql API.

We plan to change both of these defaults to None and to not
enforce any TDS protocol version by default in pymmsql 2.2.

docs/ref/pymssql.rst

@@ -29,7 +29,7 @@ Functions
 .. function:: connect(server='.', user='', password='', database='', \
                       timeout=0, login_timeout=60, charset='UTF-8', \
                       as_dict=False, host='', appname=None, port='1433',\
-                      conn_properties)
+                      conn_properties, autocommit=False, tds_version='7.1')
 
     Constructor for creating a connection to the database. Returns a
     :class:`Connection` object.
@@ -58,6 +58,10 @@ Functions
                               establishment. Can be a string or another kind
                               of iterable of strings. Default value: See
                               :class:`_mssql.connect <_mssql.MSSQLConnection>`
+    :keyword autocommit: Whether to use default autocommiting mode or not
+    :type autocommit: boolean
+    :keyword tds_version: TDS protocol version to use.
+    :type tds_version: string
 
     .. warning::
         Currently, setting *timeout* or *login_timeout* have a process-wide
@@ -77,6 +81,12 @@ Functions
     .. versionadded:: 2.1.1
         The *conn_properties* argument.
 
+    .. versionadded:: 2.1.1
+        The *autocommit* argument.
+
+    .. versionadded:: 2.1.2
+        The *tds_version* argument.
+
 .. function:: get_dbversion()
 
     TBD

pymssql.pyx

@@ -584,7 +584,7 @@ cdef class Cursor:
 
 def connect(server='.', user='', password='', database='', timeout=0,
         login_timeout=60, charset='UTF-8', as_dict=False,
-        host='', appname=None, port='1433', conn_properties=None, autocommit=False):
+        host='', appname=None, port='1433', conn_properties=None, autocommit=False, tds_version='7.1'):
     """
     Constructor for creating a connection to the database. Returns a
     Connection object.
@@ -612,8 +612,10 @@ def connect(server='.', user='', password='', database='', timeout=0,
     :keyword conn_properties: SQL queries to send to the server upon connection
                               establishment. Can be a string or another kind
                               of iterable of strings
-    :keyword autocommit whether to use default autocommiting mode or not
+    :keyword autocommit: Whether to use default autocommiting mode or not
     :type autocommit: boolean
+    :keyword tds_version: TDS protocol version to use.
+    :type tds_version: string
     """
 
     # set the login timeout
@@ -636,7 +638,7 @@ def connect(server='.', user='', password='', database='', timeout=0,
     try:
         conn = _mssql.connect(server=server, user=user, password=password,
                               charset=charset, database=database,
-                              appname=appname, port=port,
+                              appname=appname, port=port, tds_version=tds_version,
                               conn_properties=conn_properties)
 
     except _mssql.MSSQLDatabaseException, e: