Post-review fixes

pre_commit_hooks/trailing_whitespace_fixer.py

diff --git a/pre_commit_hooks/trailing_whitespace_fixer.py b/pre_commit_hooks/trailing_whitespace_fixer.py
index 7ac5479..fa9b7dd 100644
--- a/pre_commit_hooks/trailing_whitespace_fixer.py
+++ b/pre_commit_hooks/trailing_whitespace_fixer.py
@@ -3,26 +3,25 @@
 import argparse
 import os
 import sys
-import tempfile
 
 from pre_commit_hooks.util import cmd_output
 
 
-def _fix_file(filename, markdown=False):
-    with tempfile.NamedTemporaryFile(mode='w+b', delete=False) as tmp_file:
-        with open(filename, mode='rb') as original_file:
-            for line in original_file.readlines():
-                # preserve trailing two-space for non-blank lines in markdown files
-                eol = b'\r\n' if line[-2:] == b'\r\n' else b'\n'
-                if markdown and (not line.isspace()) and line.endswith(b'  ' + eol):
-                    line = line.rstrip(b' \r\n')  # restricted stripping: e.g. \t are not stripped
-                    # only preserve if there are no trailing tabs or unusual whitespace
-                    if not line[-1:].isspace():
-                        tmp_file.write(line + b'  ' + eol)
-                        continue
-                tmp_file.write(line.rstrip() + eol)
-    os.remove(filename)
-    os.rename(tmp_file.name, filename)
+def _fix_file(filename, is_markdown):
+    with open(filename, mode='rb') as file_processed:
+        lines = file_processed.readlines()
+    lines = [_process_line(line, is_markdown) for line in lines]
+    with open(filename, mode='wb') as file_processed:
+        for line in lines:
+            file_processed.write(line)
+
+
+def _process_line(line, is_markdown):
+    # preserve trailing two-space for non-blank lines in markdown files
+    eol = b'\r\n' if line[-2:] == b'\r\n' else b'\n'
+    if is_markdown and (not line.isspace()) and line.endswith(b'  ' + eol):
+        return line.rstrip() + b'  ' + eol
+    return line.rstrip() + eol
 
 
 def fix_trailing_whitespace(argv=None):

tests/trailing_whitespace_fixer_test.py

diff --git a/tests/trailing_whitespace_fixer_test.py b/tests/trailing_whitespace_fixer_test.py
index 3498edd..3a72ccb 100644
--- a/tests/trailing_whitespace_fixer_test.py
+++ b/tests/trailing_whitespace_fixer_test.py
@@ -42,7 +42,7 @@
 MD_TESTS_2 = (
     ('foo.txt', 'foo  \nbar \n  \n', 'foo  \nbar\n\n'),
     ('bar.Markdown', 'bar   \nbaz\t\n\t\n', 'bar  \nbaz\n\n'),
-    ('bar.MD', 'bar   \nbaz\t   \n\t\n', 'bar  \nbaz\n\n'),
+    ('bar.MD', 'bar   \nbaz\t   \n\t\n', 'bar  \nbaz  \n\n'),
     ('.txt', 'baz   \nquux  \t\n\t\n', 'baz\nquux\n\n'),
     ('txt', 'foo   \nbaz \n\t\n', 'foo\nbaz\n\n'),
 )