Fix example IGNORE patterns (django-webpack#179)

Needs to be a raw string otherwise it contains invalid escapes.

Author: OrangeDog

README.md

@@ -90,7 +90,7 @@ WEBPACK_LOADER = {
  'STATS_FILE': os.path.join(BASE_DIR, 'webpack-stats.json'),
  'POLL_INTERVAL': 0.1,
  'TIMEOUT': None,
- 'IGNORE': ['.+\.hot-update.js', '.+\.map']
+ 'IGNORE': [r'.+\.hot-update.js', r'.+\.map']
  }
 }
 ```