Stale table cache casues incorrect results

[gregnavis]

The following code snippet demonstrates the issue:

import dataset

db = dataset.connect('sqlite:///:memory:')

# We create test_table and insert a single row into it
t1 = db.get_table('test_table')
t1.insert(dict(key='value'))

# We access the table with a different Table object and we cannot see the
# property named key that we added above
t2 = db.get_table('test_table')
print list(t2.all()) # [OrderedDict([(u'id', 1)])]

The problem occurs only when accessing the data through two different Table objects.

PS I cheated a little bit because added break at the end of the loop in Table.find - without it Table.all() never returns. However the problem described above appears in the version uploaded to PyPI too.