Using build to build the sdist and wheel files

[Usman2ABN]

No description provided.

[mbyrnepr2]

Changes look perfect.
The CI failures are as expected but need fixing. The root-cause as described in #196.
The setup.py which references the requirements.txt is breaking the sdist. One solution could be to include requirements.txt in a MANIFEST.in but I would consider the approach taken in the wizard (refactored out the requirements.txt entirely).

[mbyrnepr2]

This should also fix/close #181 btw.

[mbyrnepr2]

The latest CI failures seem to stem from the setup.cfg of the backend - Celery and its transitory dependencies install fine but every top-level dep after celery here is not installed. Looks like the indentation is off.

Other than that - I think we shouldn't pin these dependencies so tightly like this, because then we run into what is discussed in #181. But we can open a separate issue to tackle that if you prefer (I envisage it to end up like the setup.cfg/setup.py of the wizard where a range of versions are acceptable and not one specific version for each dependency - with the latter making it more likely that other packages in the same environment as resc will have conflicting package versions (since they have their own dependency requirements).

[mbyrnepr2]

FYI added #201 so we can separate the version-pinning refactor into a different PR.

This should also fix/close #181 btw.