No module named 'Cython'

Hi there, first of all thanks for the project!

Somehow I struggle to install it when using Windows + Miniconda.

(C:\path\to\miniconda)` C:\current\directory>pip install pykrige
Collecting pykrige
  Downloading PyKrige-1.3.0.tar.gz (596kB)
    100% |████████████████████████████████| 604kB 1.5MB/s
    Complete output from command python setup.py egg_info:
        Traceback (most recent call last):
          File "<string>", line 1, in <module>
          File "C:\Users\current-user\AppData\Local\Temp\pip-build-phddipzi\pykrige\setup.py", line 14, in <module>
        from Cython.Distutils import build_ext
    ModuleNotFoundError: No module named 'Cython'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in C:\Users\current-user\AppData\Local\Temp\pip-build-phddipzi\pykrige\