Loader command bug fixes

* Fix load_status and cancel_load arg parsers
* add more load status completion values

Co-authored-by: Austin Kline <[email protected]>

remove query_mode line magic (aws#33)

Co-authored-by: Austin Kline <[email protected]>

austinkline/windows (aws#6)

* Windows Compatibility

- Fix path generation to permit windows compatibility
- use `pip install -e .` when installing for unit and integration tests
- add install hooks for nbextensions using jupyter install syntax
- fix bug causing datetimes to not be serialized properly from Neptune

Co-authored-by: Austin Kline <[email protected]>

Sagemaker Compatibility (aws#4)

Co-authored-by: Austin Kline <[email protected]>

Port to github (aws#3)

* Port to github.

- magic commands to connect to graph endpoints using gremlinpython for TinkerPop and SPARQLWrapper/requests for SPARQL
- magic commands for connecting to Neptune-specific api paths
- custom widget for visualizing graph results.
- premade starter notebooks to walk through notebook functionality
- seed datasets to load data into Tinkerpop or SPARQL for trying out graph

Co-authored-by: Austin Kline <austinkline@>