UUID field class absent

ClickHouse added new data type UUID:
https://github.com/yandex/ClickHouse/blob/master/CHANGELOG.md#clickhouse-release-1154276

sqlalchemy-clickhouse raises following error when trying to open table with UUID fields in Superset:
```
ERROR:root:No field class for UUID
Traceback (most recent call last):
File "/root/superset/lib/python2.7/site-packages/superset/sql_lab.py", line 180, in execute_sql
query.executed_sql, **db_engine_spec.cursor_execute_kwargs)
File "/root/superset/lib/python2.7/site-packages/sqlalchemy_clickhouse/connector.py", line 200, in execute
self._process_response(response)
File "/root/superset/lib/python2.7/site-packages/sqlalchemy_clickhouse/connector.py", line 331, in _process_response
for r in response:
File "/root/superset/lib/python2.7/site-packages/infi/clickhouse_orm/database.py", line 162, in select
model_class = model_class or ModelBase.create_ad_hoc_model(zip(field_names, field_types))
File "/root/superset/lib/python2.7/site-packages/infi/clickhouse_orm/models.py", line 47, in create_ad_hoc_model
attrs[name] = cls.create_ad_hoc_field(db_type)
File "/root/superset/lib/python2.7/site-packages/sqlalchemy_clickhouse/connector.py", line 82, in create_ad_hoc_field
raise NotImplementedError('No field class for %s' % db_type)
NotImplementedError: No field class for UUID
```