Dotifi requirements.txt sets specific version of nipyapi, preventing upgrades

[ChrisSamo632]

Describe the bug
Installing dotifi alongside nipyapi (where nipyapi is installed already on a system/through the same requirements.txt) warns about mismatching dependency versions and that python/pip will prevent this in the future.

To Reproduce
pip install -r requirements.txt

requirements.txt contains:

nipyapi>=0.16.2,<0.17
dotifi>=0.2.1,<1.0.0

Expected behavior
pip install doesn't complain and all packages are installed.

Appreciate this is a little tricky because you can't guarantee that dotifi will remain compatible with future versions of nipyapi, but is it better to allow for a dependency to be "at least" a known-good version?

Desktop (please complete the following information):
- OS: Ubuntu VERSION: 20.10 (although using the python docker base image from Docker Hub to build an image containing nipyapi & dotifi)
- NIFI: 1.11.4 (but preparing to upgrade to 1.13.0, hence the jump in nipyapi version)
- Python: 3.9
- dotifi: 0.2.1

Logs

	ERROR: Cannot install -r /usr/src/app/requirements.txt (line 3) and nipyapi<0.17 and >=0.16.2 because these package versions have conflicting dependencies.
	
	The conflict is caused by:
	    The user requested nipyapi<0.17 and >=0.16.2
	    dotifi 0.2.1 depends on nipyapi<0.15.0 and >=0.14.3
	
	To fix this you could try to:
	1. loosen the range of package versions you've specified
	2. remove package versions to allow pip attempt to solve the dependency conflict
	
	ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/user_guide/#fixing-conflicting-dependencies
	The command '/bin/sh -c pip install --no-cache-dir -r "${APP_DIR}/requirements.txt"' returned a non-zero code: 1