Provide automatic removal of pkg-resources==0.0.0

Should help to deal with that pretty paintuly issue under Ubuntu/Debian
family:
https://bugs.launchpad.net/ubuntu/+source/python-pip/+bug/1635463
diff --git a/pre_commit_hooks/requirements_txt_fixer.py b/pre_commit_hooks/requirements_txt_fixer.py
index 1ee6fac..623fede 100644
--- a/pre_commit_hooks/requirements_txt_fixer.py
+++ b/pre_commit_hooks/requirements_txt_fixer.py
@@ -69,6 +69,11 @@
     else:
         rest = []
 
+    for requirement in requirements:
+        if b'pkg-resources' in requirement.name:
+            if b'0.0.0' in requirement.value:
+                requirements.remove(requirement)
+
     for requirement in sorted(requirements):
         after.extend(requirement.comments)
         after.append(requirement.value)