Merge branch 'rework-commands-system' into work-on-hmget-hmset

Conflicts:
	limpyd/fields.py
Move redis_connect to database module (fix #49 issue)

`import redis` in the __init__.py file make the setup.py not
loadable without redis lib already installed.
Merge pull request #43 from twidi/rework-commands-system

Rework commands system
Merge branch 'rework-commands-system' into work-on-hmget-hmset

Conflicts:
	limpyd/fields.py
	limpyd/utils.py
Move TEST_CONNECTION_SETTINGS to tests/base.py
Revert "hgmet & hmset can know accept args as in redis-py"

This reverts commit 912d4b1cda1a9aeaa1fb619d0e8387e4e959d8a3.

Conflicts:

	tests/model.py
Revert "Update doc about arguments for hmget and hmset"

This reverts commit 0e2f430d04412c1d8cabe58b4798f51d1974cbb9.
Make "redis_connect" a method of Database
Merge pull request #51 from yohanboniface/move_redis_connect

Move redis_connect to database module (fix #49 issue)
Merge pull request #52 from twidi/work-on-hmget-hmset

Work on hmget hmset
Merge branch 'master' into enhance-collections

Conflicts:
	limpyd/fields.py
	limpyd/model.py
	limpyd/utils.py
Add a lazy_connect classmethod to the model

And then replace calls to the constructor with the _skip_exist_test to
calls to this new class method.
Add a connect method to RedisModel

(and use it in call_command instead of using the _update_running var)
Add docstring to RedisModel.connect
Merge pull request #53 from twidi/enhance-collections

Enhance collections
Merge branch 'master' into enhance-related