Fixes #88 - Invalid URL with empty filter()

Raise a ValueError when kwargs for filter() is empty to keep a uniform API and prevent the issues seen in issue #88.

pynetbox/lib/endpoint.py

@@ -158,7 +158,10 @@ def get(self, *args, **kwargs):
             if len(filter_lookup) == 0:
                 return None
             else:
-                raise ValueError('get() returned more than one result.')
+                raise ValueError(
+                    'get() returned more than one result.'
+                    'Perhaps use filter() or all() instead.'
+                )
 
         req = Request(
             key=key,
@@ -217,9 +220,14 @@ def filter(self, *args, **kwargs):
         >>>
         """
 
-        if len(args) > 0:
+        if args:
             kwargs.update({'q': args[0]})
 
+        if not kwargs:
+            raise ValueError(
+                'filter must be passed kwargs. Perhaps use all().'
+            )
+
         req = Request(
             filters=kwargs,
             base=self.url,