Pin package constraints

[dawidratynski]

Add a way to automatically pin the newest compatible package versions using pip-compile based on already present package requirements. This significantly speeds up deployment time.

This approach could potentially be better in the long run, as bumping package versions won't require manually going through all packages to change requirements, which could be an issue if only very strict requirements are present.

Closes #292

[A-dead-pixel]

Can't we somehow keep the not-pinned requirements in setup.py? pip-compile supports generating from that.

[dawidratynski]

Moved not-pinned requirements back to setup.py and recompiled requirements.