Incorporate patch to support isolated CR

diff --git a/pre_commit_hooks/end_of_file_fixer.py b/pre_commit_hooks/end_of_file_fixer.py
index 37ebbb5..5ab1b7b 100644
--- a/pre_commit_hooks/end_of_file_fixer.py
+++ b/pre_commit_hooks/end_of_file_fixer.py

@@ -15,13 +15,13 @@
         return 0
     last_character = file_obj.read(1)
     # last_character will be '' for an empty file
-    if last_character != b'\n' and last_character != b'':
+    if last_character not in {b'\n', b'\r'} and last_character != b'':
         # Needs this seek for windows, otherwise IOError
         file_obj.seek(0, os.SEEK_END)
         file_obj.write(b'\n')
         return 1
 
-    while last_character == b'\n' or last_character == b'\r':
+    while last_character in {b'\n', b'\r'}:
         # Deal with the beginning of the file
         if file_obj.tell() == 1:
             # If we've reached the beginning of the file and it is all
@@ -38,8 +38,10 @@
     # newlines.  If we find extraneous newlines, then backtrack and trim them.
     position = file_obj.tell()
     remaining = file_obj.read()
-    for sequence in [b'\n', b'\r\n']:
-        if remaining.startswith(sequence) and len(remaining) > len(sequence):
+    for sequence in (b'\n', b'\r\n', b'\r'):
+        if remaining == sequence:
+            return 0
+        elif remaining.startswith(sequence):
             file_obj.seek(position + len(sequence))
             file_obj.truncate()
             return 1

diff --git a/tests/end_of_file_fixer_test.py b/tests/end_of_file_fixer_test.py
index deedeab..f8710af 100644
--- a/tests/end_of_file_fixer_test.py
+++ b/tests/end_of_file_fixer_test.py

@@ -17,6 +17,8 @@
     (b'\xe2\x98\x83', 1, b'\xe2\x98\x83\n'),
     (b'foo\r\n', 0, b'foo\r\n'),
     (b'foo\r\n\r\n\r\n', 1, b'foo\r\n'),
+    (b'foo\r', 0, b'foo\r'),
+    (b'foo\r\r\r\r', 1, b'foo\r'),
 )