Update .travis.yml

Allow external
Merge branch 'release/2.0.0-stable'
added AssetEnvType model class + used it in device & added to admin view
better names for AssetEnvType & added migration file
added new table ServiceCatalog & used it in discovery.device
flake8 ready ;P
service_catalog inherited from cmdb.ci
better import
added utils files with object factories (for tests) & device lookups
rm unused lookup DeviceEnvironment
added factory-boy to setup.py
flake8 ready
better docstring
review impr.
Merge pull request #992 from xliiv/ser-env-fields

service & environment fields
fixed get_item_url bug
hasattr replaced with getattr
Merge pull request #994 from xliiv/ser-env-fields

fixed get_item_url bug
Added 'SyncFieldMixin' + some additional logic in order to keep selected
fields in sync between 'Device' and 'Asset' models.
Added 'service catalog' and 'environment' fields to the 'device info' form.