Added Vagrant + Ansible configuration

The `vagrant` configuration contains everything to start and provision
a testing VM. Please refer to `vagrant/README.rst` for more information.
Added deployment documentation
Enabled error logging to stdout by default
Fixed bug in EpochField

On MySQL, the type returned by the database for an EpochField is
`long`, not `int`.
Fixed wording in device delete template
Fixed "too many SQL variables" bug in SwidMeasurementView
Massive performance optimizations in inventory view
Migration scripts for TagStats model
Fixed 'too many SQL variables' in log view and added filter to log view
Fixed the 'initial measurement not shown in log view' problem
Added overflow-x: scroll to paged content
Improved CSS
Merge 'Integration Request 6'

This brings massive performance improvements, deployment docs,
configuration for a test VM (Vagrantfile) and several other improvements
and bugfixes.

To improve the performance a new database table is introduced.  To migrate
an existing SQLite database use the following steps:

1. Create the new table:

    sqlite3 /path/to/database
    sqlite> .read sql/issue294_create.sql

2. Migrate existing sessions:

    ./manage.py shell
    >>> execfile('sql/issue294_migrate.py')

Closes #13.