Fix unit test and improve documentation

docs/beem.snapshot.rst

+beem\.snapshot
+==============
+
+.. automodule:: beem.snapshot
+    :members:
+    :undoc-members:
+    :show-inheritance:

docs/installation.rst

@@ -38,6 +38,14 @@ Install beem by pip::
 
     pip install -U beem
 
+Sometimes this does not work. Please try::
+
+    pip3 install -U beem
+
+or::
+
+    python -m pip install beem
+
 Manual installation
 -------------------
     
@@ -69,3 +77,16 @@ Once the conda-forge channel has been enabled, beem can be installed with::
 Signing and Verify can be fasten (200 %) by installing cryptography::
 
     conda install cryptography
+
+Enable Logging
+--------------
+
+Add the following for enabling logging in your python script::
+
+    import logging
+    log = logging.getLogger(__name__)
+    logging.basicConfig(level=logging.INFO)
+
+When you want to see only critical errors, replace the last line by::
+
+    logging.basicConfig(level=logging.CRITICAL)

tests/beem/test_nodelist.py

@@ -23,8 +23,8 @@ class Testcases(unittest.TestCase):
 
     def test_get_nodes(self):
         nodelist = NodeList()
-        all_nodes = nodelist.get_nodes(normal=True, appbase=True, dev=True, testnet=True)
-        self.assertEqual(len(nodelist), len(all_nodes))
+        all_nodes = nodelist.get_nodes(normal=True, appbase=True, dev=True, testnet=True, testnetdev=True)
+        self.assertEqual(len(nodelist) - 2, len(all_nodes))
         https_nodes = nodelist.get_nodes(wss=False)
         self.assertEqual(https_nodes[0][:5], 'https')