use VERSION file to avoid importing gridlock before its installed

MANIFEST.in

@@ -1,2 +1,3 @@
 include README.md
 include LICENSE.md
+include gridlock/VERSION

gridlock/VERSION

@@ -0,0 +1 @@
+0.3

gridlock/__init__.py

@@ -16,10 +16,14 @@ Dependencies:
 - skimage               [Grid.visualize_isosurface()]
 """
 
+import pathlib
+
 from .error import GridError
 from .direction import Direction
 from .grid import Grid
 
 __author__ = 'Jan Petykiewicz'
 
-version = '0.3'
+with open(pathlib.Path(__file__).parent / 'VERSION', 'r') as f:
+    __version__ = f.read().strip()
+version = __version__

setup.py

@@ -1,13 +1,15 @@
 #!/usr/bin/env python3
 
 from setuptools import setup, find_packages
-import gridlock
 
 with open('README.md', 'r') as f:
     long_description = f.read()
 
+with open('gridlock/VERSION', 'r') as f:
+    version = f.read().strip()
+
 setup(name='gridlock',
-      version=gridlock.version,
+      version=version,
       description='Coupled gridding library',
       long_description=long_description,
       long_description_content_type='text/markdown',
@@ -15,6 +17,9 @@ setup(name='gridlock',
       author_email='anewusername@gmail.com',
       url='https://mpxd.net/code/jan/gridlock',
       packages=find_packages(),
+      package_data={
+          'gridlock': ['VERSION']
+      },
       install_requires=[
             'numpy',
             'float_raster',