when multi databases switched, config operation did not update the connection.
Merge branch 'master' of https://github.com/zhangguoze/CURD.py into pull-9

* 'master' of https://github.com/zhangguoze/CURD.py:
  when multi databases switched, config operation did not update the connection.
fix spaces in merge from zhangguoze/master to origin/master
table_name default be: '_' joined
changes for 0.4.1
tests for table_name
pep8 fixing, actually not all lines are pep8: width<79
release v0.4.1
documentation for v0.4.1