Update filehandling utilities

----Release Notes----
[]
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123667095

Author: robertwb

google/cloud/dataflow/io/fileio.py

@@ -282,6 +282,18 @@ def rmdir(path):
       except OSError as err:
         raise IOError(err)
 
+  @staticmethod
+  def rm(path):
+    if path.startswith('gs://'):
+      # pylint: disable=g-import-not-at-top
+      from google.cloud.dataflow.io import gcsio
+      gcsio.GcsIO().delete(path)
+    else:
+      try:
+        os.remove(path)
+      except OSError as err:
+        raise IOError(err)
+
   @staticmethod
   def glob(path):
     if path.startswith('gs://'):