[fix] Use the autolimit config parameter, as specified in the documentation. Fix #9
[mod] Remove unused imports
[enh] Use the Ipython system to handle config.

This allow configuration parameters to be inspected directly in
IPython using the %magic
[fix] Retain config set in profile
[enh] Document the parameters in the config

This way they can be seen with %config
[enh] Define the configuration directly on the Magic

As documented on https://github.com/ipython/ipython/issues/4206
Had to rename SQLMagics to SqlMagic to keep compability with current config.
[mod] Move execute back into SqlMagic

Made more sense than passing self twice.
Also test the magic directly using Ipython facilities
[test] Added a test for the autolimit parameter
Merge pull request #11 from olethanh/use_ipython_config

Use ipython configuration system