numpy not included in install_requires

[duncanmmacleod]

This package requires numpy to import the top-level module, but this is not included in the install_requires metadata for setuptools:

$ python3 -m venv tmp && ./tmp/bin/pip install declarative && ./tmp/bin/python -c "import declarative"
Collecting declarative
  Downloading declarative-1.3.0-py2.py3-none-any.whl (48 kB)
     |████████████████████████████████| 48 kB 2.0 MB/s
Installing collected packages: declarative
Successfully installed declarative-1.3.0
WARNING: You are using pip version 20.2.1; however, version 21.0.1 is available.
You should consider upgrading via the '/home/duncan/tmp/tmp/bin/python3 -m pip install --upgrade pip' command.
/home/duncan/tmp/tmp/lib/python3.8/site-packages/declarative/utilities/representations.py:8: DeprecationWarning: Compatibility support for python2 has been dropped
  from ..utilities.future_from_2 import repr_compat
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/duncan/tmp/tmp/lib/python3.8/site-packages/declarative/__init__.py", line 24, in <module>
    from .callbacks import (
  File "/home/duncan/tmp/tmp/lib/python3.8/site-packages/declarative/callbacks/__init__.py", line 11, in <module>
    from .relay import (
  File "/home/duncan/tmp/tmp/lib/python3.8/site-packages/declarative/callbacks/relay.py", line 6, in <module>
    import numpy as np
ModuleNotFoundError: No module named 'numpy'