Prevent MemoryFS.removedir(..., recursive=True) removing non-empty parent…

Prevent MemoryFS.removedir(..., recursive=True) removing non-empty parent directories, and fixed up corresponding unit test.
Fixes Issue 137

fs/memoryfs.py

@@ -484,6 +484,9 @@ class MemoryFS(FS):
                 if not dirname:
                     raise RemoveRootError(path)
                 del parent_dir.contents[dirname]
+                # stop recursing if the directory has other contents
+                if parent_dir.contents:
+                    break
         else:
             pathname, dirname = pathsplit(path)
             parent_dir = self._get_dir_entry(pathname)

fs/tests/__init__.py

@@ -419,6 +419,7 @@ class FSTestCases(object):
         self.fs.removedir("foo/bar/baz", recursive=True)
         self.assert_(not check("foo/bar/baz"))
         self.assert_(not check("foo/bar"))
+        self.assert_(check("foo/file.txt"))
         #  Ensure that force=True works as expected
         self.fs.makedir("frollic/waggle", recursive=True)
         self.fs.setcontents("frollic/waddle.txt",b("waddlewaddlewaddle"))