generalized the pprint interface so that it can be overloaded in derived classes
Added the creation of the __timestamp__ reserved entity
run coverage tests with Tox
Touch the timestamp of an entity at each CUD operation.

Added the decorator for updating the timestamp of the last modification to
a group of entities. No global lock is in place so it may happen something
goes wrong under fast updates. However, we are keeping the timestamp with
seconds granularity right now.
Added the methods to get the timestamp as well.
Timestamp feature and tests.

With a small change to preceding versions, now we use a "number" to store the timestamp data, as we need a little more fine-grain
and there is no reason to lose information at this stage.
Merge branch 'timestamp' of git.autistici.org:configdb
get_timestamp(): Raise ValueError when no timestamp is present.

Before, we raised a configdb.exceptions.NotFound which could be confusing when debugging.
disable doozer/zk tests using environment variables
minor style/whitespace fixes
sleep a tiny bit before checking for timestamp increment
prevent a UnicodeDecodeError in find_all - fixes issue #12
Fixed the de-serialization of relations coming from Leveldb interface
added a test for names with slashes (WiP)
Fixing issue with two-way referenced relations in the sqlalchemy interface (closes issue #13)
Final fix for issue12
(Failing) tests for entities containing a slash in the name
Fix for slashes in entities name
Version bump