Neomodel

* Dropped Python 2.7 support
* Included support for Neo4j 4.*
* Updated spatial PointProperty to better reflect the native data type
* Updated Database housekeeping functions (drop_constraints(), drop_indexes(), install_labels())
* Updated all underlying queries to better reflect current CYPHER
* Updated Transaction handling
* Updated tests
* Many thanks to Cristina Escalante, Matt Galvis, JVemmer and a-takahashi223 whose hard work made this release possible.

* Fixed validation for unique properties to also be optional (470) - Jon Daly
* Fixed tests-with-docker-compose.sh (452) - Jorge Valhondo Rama
* Added exclusion example to documentation and improved naming consistency (456, 466) - Elena Williams
* Fixed the Travis-CI build problems by switching to openjdk (471) - Duncan Booth
* Minor revisions in `test_set_connection`, `spatial datatypes` and documentation (442, 446, 447) - Athanasios Anastasiou
* Added `max_length` constraint on `StringProperty` (445) - Lazy-Y
* Upgraded neo4j python driver requirement to 1.7.2 (432) - Robert Grant
* Added a `DateTimeFormatProperty` (428) - Yu Shengnan
* Updated `setup.py` so that it excludes the `test/` and `test/test_contrib/` sub-packages (426) - Jorge Valhondo Rama
* Updated getting_started.rst typo (419) - fredthehead
* Fixed NeomodelPoint instantiation bug (418) - Athanasios Anastasiou

* Fixed a number of warnings due to deprecations both within neomodel and pytest and overall improvements in
code style (381) - Abhishek Modi
* Added support for spatial data through neomodel.contrib.spatial_datatypes (384) - Athanasios Anastasiou
* Added the ability to filter "left-hand statements" (in NodeSet expressions) too (395) - Grzegorz Grzywacz
* Refactor the Node Class Registry to make util.Database a true Singleton (403) - Giorgos Oikonomou
* Many thanks to Giorgos Oikonomou, Jon Daly, Adam Romano, Andrew Tergis, Mato Žgajner, Mostafa Moradian, mjmare,
Phoebe Bright, Robert Grant, jberends and anyone else who helped flag, track and correct this bug. For more
information, please see: https://github.com/neo4j-contrib/neomodel/issues/378
* Added the ClassAlreadyDefined exception to prevent against accidental redefinitions of data model classes (409)
- Athanasios Anastasiou
* Added the ability to lazily `.nodes.get()` and `.nodes.all()` (406) - Matan Hart
* Fixed a bug in the assumed direction of relationships in _build_merge_query (408) - MrAnde7son

* Added support for Q() in filter and exclude (360) - Juan H. Hidalgo
* Added object docs and examples - Juan H. Hidalgo
* Raise DoesNotExist when refreshing a non existent inflated node (355) - lerela
* Empty filter bug - Mardanov Timur Rustemovich
* Closed 361 Nodes connected with two or more relationships - Mardanov Timur Rustemovich
* Exclude method fixed - Mardanov Timur Rustemovich
* Filter with OR fixed - Mardanov Timur Rustemovich
* Resolved 283, improved object resolution of cypher_query so that it
resolves objects even if they are nested within lists. Overall
documentation edits - Athanasios Anastasiou

* Add check for wiping db on test run - Athanasios
* Correct function name in doc string - Henry Jordan
* Support filtering on properties that end with a hash (348) - mprahl
* Support neo4j-driver v1.6.0 (347) - mprahl
* Explicit write transaction mode (337) - Robert Grant
* Adds a check for Traversal's definition argument (333) - Frank Sachsenheim

* Fix syntax error in import