Update installation dependencies

README.md

@@ -32,7 +32,7 @@ Installation
 
 **Prerequisites**:
   * **Python**: Available for python 3.6 to 3.8 (limited by current compatibility issues with Numba)
-  * [NumPy](https://numpy.org): needed for running setup (distutils). Follow instructions outlined [here](https://docs.scipy.org/doc/numpy/user/install.html) for installation.
+  * [NumPy](https://numpy.org): If using cython, numpy is needed for running setup (distutils). Follow instructions outlined [here](https://docs.scipy.org/doc/numpy/user/install.html) for installation.
 
 Options
 =======

docs/getting_started.rst

@@ -8,7 +8,7 @@ Install Package
 
 **Prerequisites:**
   * **Python**: Available for python 3.6 to 3.8 (limited by current compatibility issues with Numba)
-  * `NumPy <https://numpy.org>`_: needed for running setup (distutils). Follow instructions outlined `here <https://docs.scipy.org/doc/numpy/user/install.html>`_ for installation.
+  * `NumPy <https://numpy.org>`_: If cython is used, numpy is needed for running setup (distutils). Follow instructions outlined `here <https://docs.scipy.org/doc/numpy/user/install.html>`_ for installation.
 
 **Option 1:** Install from pip: ``pip install despasito``
 

setup.py

@@ -7,7 +7,6 @@
 from setuptools import find_packages, Extension, setup
 import versioneer
 import glob
-import numpy as np
 
 short_description = __doc__.split("\n")
 fpath = os.path.join("despasito", "equations_of_state", "saft", "compiled_modules")
@@ -23,6 +22,7 @@
     flag_cython = False
 
 if flag_cython:
+    import numpy as np
     cython_list = glob.glob(os.path.join(fpath, "*.pyx"))
     for cyext in cython_list:
         name = os.path.split(cyext)[-1].split(".")[-2]