Support override variables

[milonimrod]

This is a PR for #5 .
The current open item is that I didn't add the functionality into the ipython support

[coveralls]

Coverage increased (+0.2%) to 82.609% when pulling 8d94c30 on milonimrod:support_override_variables into 5e839d4 on theskumar:master.

[coveralls]

Coverage increased (+0.2%) to 82.609% when pulling ee6bde5 on milonimrod:support_override_variables into 5e839d4 on theskumar:master.

[coveralls]

Coverage increased (+0.4%) to 82.813% when pulling d4f3243 on milonimrod:support_override_variables into 5e839d4 on theskumar:master.

[coveralls]

Coverage increased (+3.5%) to 85.938% when pulling 249cbdd on milonimrod:support_override_variables into 5e839d4 on theskumar:master.

[milonimrod]

Please notice that on commit 249cbdd I added a general case test for the IPython magic (regardless of the override option)

[theskumar]

Thanks for pull request. I'll take a look.

[coveralls]

Coverage increased (+3.5%) to 86.01% when pulling 41bbd1a on milonimrod:support_override_variables into 3aa526c on theskumar:master.

[theskumar]

This looks super good feature to go in. IPython support with override -o argument needs to be documented. Happy to merge and release a new build with updated docs. 👍

[theskumar]

I've also resolved a merge conflict with web UI for this branch/PR, but not sure how Github would reflect that on your side. If you face any problem let me know, i'll update the docs on my end.

[milonimrod]

No problem. I'll pull the new master, merge them and add the documentation (also, I'll add the support for the verbose on the IPython side)