Force to analyze mailing lists or directories with only one archive
Use get_database instead of create database
dbn: Add new database module/definition using SqlAlchemy
dbn: Add session implementation to integrate the new database
dbn: Add class Report for generating reports from the database
Integration of SqlAlchemy classes in mlstats
ci: Update .travis.yml for continuous integration
dbn: Remove unused methods
Remove old database code
db: Move new database implementation in the old namespace

Last step to replace the old database implementation with
SqlAlchemy
db: Force convert to unicode for MySQL dialect
Simplify logging information
Remove admin parameters to the create database

Since SqlAlchemy, we will rely on the user to create the
database, though we will create the tables if they don't
exists. Therefore, this option does not makes sense anymore.
tests: Update tests according to latest changes in analyzer

We now returns a datetime instead of a ISO string, therefore,
the test should reflect that comparison
setup: Update meta data
database: add mailing_list_url to primary key in messages table

This change on the database schema allows to store messages
that were sent to different mailing lists.

Applied this change according to commit ad6e5a48 done in the
old database code base.