Explicit exports from the timescale.db.models module

[schlunsen]

No description provided.

[schlunsen]

Still needs testing!

Allows for django like imports:

from timescale.db.models as tsdb
tsdb.TimescaleDateTimeField()

See bencleary#2

[bencleary]

I have been able to finally work on this now, I need a little more time to finish the docs, types and update my branches and organise it a little more before but the package can now be access as import timescale.db.models as tsdb or from timescale.db.models.fields import TimescaleDateTimeField.

As part of this the TimescaleModel has been moved to a utils package due to the idea of what the TimescaleModel represented of a utility class that groups the pieces together.

I am still working on a test suite, and planning out what needs to be tested and how we test it.