move nested_lookup into a module

modified:   README.rst
	new file:   nested_lookup/__init__.py
	renamed:    nested_lookup.py -> nested_lookup/nested_lookup.py
	modified:   setup.py

nested_lookup/__init__.py

@@ -0,0 +1 @@
+from nested_lookup import nested_lookup

nested_lookup/nested_lookup.py

@@ -0,0 +1,25 @@
+from six import iteritems
+
+def nested_lookup(key, document):
+    """Lookup a key in a nested document, return a list of values"""
+    return list(_nested_lookup(key, document))
+
+def _nested_lookup(key, document):
+    """Lookup a key in a nested document, yield a value"""
+    if isinstance(document, list):
+        for d in document:
+            for result in _nested_lookup(key, d):
+                yield result
+
+    if isinstance(document, dict):
+        for k, v in iteritems(document):
+            if k == key:
+                yield v
+            elif isinstance(v, dict):
+                for result in _nested_lookup(key, v):
+                    yield result
+            elif isinstance(v, list):
+                for d in v:
+                    for result in _nested_lookup(key, d):
+                        yield result
+