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.py

@@ -1,25 +0,0 @@
-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
-