Added version number to pystencils

Pystencils should have a __version__ attribute

pystencils/__init__.py

 """Module to generate stencil kernels in C or CUDA using sympy expressions and call them as Python functions"""
+import os.path
 from . import sympy_gmpy_bug_workaround  # NOQA
 from . import fd
 from . import stencil as stencil
@@ -21,6 +22,13 @@ try:
 except ImportError:
     pass
 
+try:
+    my_path = os.path.abspath(os.path.dirname(__file__))
+    path = os.path.join(my_path, '../RELEASE-VERSION')
+    __version__ = open(path, 'r').read()
+except IOError:
+    __version__ = 'Please install pystencils with setup.py'
+
 __all__ = ['Field', 'FieldType', 'fields',
            'TypedSymbol',
            'make_slice',