Support `autocommit=True` for constructor argument.
Merge branch 'master' of https://github.com/farcepest/MySQLdb1 into autocommit_on
autocommit=None means using server default.
Fix typo.
'BEGIN' on __enter__ if autocommit is enabled.
Merge pull request #12 from KLab/autocommit_on

Support keyword argument to initially autocommit=on