Added database storing option

Replace all emoticons with their title, to be included in the tweet text

Added some loop around, it seams that could slow down but not because with elasticsearch you can index about 6k items/s so the performance is not affected (in most cases). 

it seams that exporting dashboard and visualization does not work, so people will have to write new ones. Pretty easy, I'll add a short tutorial.

How-to-setup Elasticsearch (dashboard still missing)

Added two tables: users and tweets.
The first stores: who, when, how much. The second stores every tweet.
If the tweet is already stored it skips to the next one so no duplication.

Added elasticsearch fun stuff

- Removed Changelog section
- Added quote specification
- Added thanks section

Update README.md

add precisions to the -g option

Update tweep.py

Tweep.py would generate an error on -g option if used as unique argument.