Editable installation does not include the OED spec

[carlfischerjba]

Issue Description

When installing ods-tools with pip install --editable .[extra] the OED spec json file is not installed. This causes the command ods_tools check to fail:

$ ods_tools check --location oed_location_1000.csv 
Traceback (most recent call last):
  File "/home/carl/venvs/myvenv/bin/ods_tools", line 33, in <module>
    sys.exit(load_entry_point('ods-tools', 'console_scripts', 'ods_tools')())
  File "/home/carl/repos/ODS_Tools/ods_tools/main.py", line 206, in main
    command_action[kwargs.pop('command')](** kwargs)
  File "/home/carl/repos/ODS_Tools/ods_tools/main.py", line 53, in check
    oed_exposure = get_oed_exposure(**extract_exposure_args(kwargs))
  File "/home/carl/repos/ODS_Tools/ods_tools/main.py", line 33, in get_oed_exposure
    return OedExposure(**kwargs)
  File "/home/carl/repos/ODS_Tools/ods_tools/oed/exposure.py", line 72, in __init__
    self.oed_schema = OedSchema.from_oed_schema_info(oed_schema_info)
  File "/home/carl/repos/ODS_Tools/ods_tools/oed/oed_schema.py", line 77, in from_oed_schema_info
    return cls.from_json(cls.DEFAULT_ODS_SCHEMA_PATH)
  File "/home/carl/repos/ODS_Tools/ods_tools/oed/oed_schema.py", line 91, in from_json
    with open(oed_json) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/home/carl/repos/ODS_Tools/ods_tools/data/OpenExposureData_Spec.json'

This is particularly awkward because #151 requires us to use an editable install in order to get other files.

Steps to Reproduce (Bugs only)

Version / Environment information

• ods-tools 3.2.7

Example data / logs