Use fatamorgana/VERSION file to single-source version number

`import fatamorgana` inside setup.py could break if dependencies weren't
satisfied

MANIFEST.in

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

fatamorgana/VERSION

@@ -0,0 +1 @@
+0.4

fatamorgana/__init__.py

@@ -18,6 +18,8 @@
     - Python 3.5 or later
     - numpy (optional, no additional functionality)
 """
+import pathlib
+
 from .main import OasisLayout, Cell, XName
 from .basic import NString, AString, Validation, OffsetTable, OffsetEntry, \
         EOFError, SignedError, InvalidDataError, InvalidRecordError
@@ -25,4 +27,7 @@ from .basic import NString, AString, Validation, OffsetTable, OffsetEntry, \
 
 __author__ = 'Jan Petykiewicz'
 
-version = '0.4'
+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 fatamorgana
 
 with open('README.md', 'r') as f:
     long_description = f.read()
 
+with open('fatamorgana/VERSION', 'r') as f:
+    version = f.read().strip()
+
 setup(name='fatamorgana',
-      version=fatamorgana.version,
+      version=version,
       description='OASIS layout format parser and writer',
       long_description=long_description,
       long_description_content_type='text/markdown',
@@ -51,6 +53,9 @@ setup(name='fatamorgana',
             'Topic :: Software Development :: Libraries :: Python Modules',
       ],
       packages=find_packages(),
+      package_data={
+          'fatamorgana': ['VERSION']
+      },
       install_requires=[
             'typing',
       ],