Fix #10: Add jinja2 to pystencils's dependencies

Alternative would be remove jinja2 (see other PR). However, I think dependency on jinja2 is not to heavy. This could make some implementations more elegant.

setup.py

@@ -86,7 +86,7 @@ setup(name='pystencils',
       author_email='martin.bauer@fau.de',
       url='https://i10git.cs.fau.de/pycodegen/pystencils/',
       packages=['pystencils'] + ['pystencils.' + s for s in find_packages('pystencils')],
-      install_requires=['sympy>=1.1', 'numpy', 'appdirs', 'joblib'],
+      install_requires=['sympy>=1.1', 'numpy', 'appdirs', 'joblib', 'jinja2'],
       package_data={'pystencils': ['include/*.h', 'backends/cuda_known_functions.txt']},
       ext_modules = cython_extensions("pystencils.boundaries.createindexlistcython"),
       classifiers=[