specify and document dependencies

README.md

@@ -18,7 +18,8 @@ TBD
 
 acme-updater is developed for python 3.x. It might work on older versions but this is not supported. Additionally, the following python modules are required:
 
-TBD
+* pyOpenSSL
+* dnspython
 
 ## COPYING
 

setup.py

@@ -13,5 +13,6 @@ setup(
     license="GNU General Public License version 2",
     packages=["amulib"],
     scripts=["acme-updater"],
-    url="https://git.cyber-everything.de/Hoshpak/acme-updater"
+    url="https://git.cyber-everything.de/Hoshpak/acme-updater",
+    install_requires=["pyOpenSSL", "dnspython"]
 )