hwi issue

In encounter the following error attempting to install HWI using Poetry on Windows 10:

```
$ poetry install
...
$ poetry shell
$ hwi enumerate
Traceback (most recent call last):
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\HWI-py3.7\Scripts\hwi-script.py", line 6, in <module>
    from pkg_resources import load_entry_point
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 3191, in <module>
    @_call_aside
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 3175, in _call_aside
    f(*args, **kwargs)
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 3204, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 583, in _build_master
    ws.require(__requires__)
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 900, in require
    needed = self.resolve(parse_requirements(requirements))
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\hwi-py3.7\lib\site-packages\pkg_resources\__init__.py", line 786, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'hwi' distribution was not found and is required by the application
$ python
>>> from hwilib import commands
>>> commands.enumerate()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\justin\dev\HWI\hwilib\commands.py", line 38, in enumerate
    imported_dev = importlib.import_module('.devices.' + module, __package__)
  File "C:\Users\justin\AppData\Local\Programs\Python\Python37-32\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Users\justin\dev\HWI\hwilib\devices\trezor.py", line 15, in <module>
    from usb1 import USBErrorNoDevice
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\HWI-py3.7\lib\site-packages\usb1\__init__.py", line 61, in <module>
    from . import libusb1
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\HWI-py3.7\lib\site-packages\usb1\libusb1.py", line 199, in <module>
    libusb = _loadLibrary()
  File "C:\Users\justin\AppData\Local\pypoetry\Cache\virtualenvs\HWI-py3.7\lib\site-packages\usb1\libusb1.py", line 173, in _loadLibrary
    return dll_loader('libusb-1.0' + suffix, **loader_kw)
  File "C:\Users\justin\AppData\Local\Programs\Python\Python37-32\lib\ctypes\__init__.py", line 364, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: [WinError 126] The specified module could not be found
```

Don't know what the first error means. The second error seems to indicate that libusb dll is missing (having trouble figuring out how to install this dll ...). If a libusb dll is required