Update setup.py

Added runtime requirements to setup.py so pip will install them automatically when the package is installed

setup.py

@@ -19,5 +19,10 @@ setup(
     author_email='llohse@uni-goettingen.de',
     url='https://gitlab.gwdg.de/irp/tmmsolve',
     packages=['tmmsolve'],
-    cmake_install_dir='tmmsolve/'
+    cmake_install_dir='tmmsolve/',
+    install_requires=[
+      'cxroots',
+      'scipy',
+      'numpy'
+    ]
   )