fix test.base.py to extent unittest.TestCase

Author: wtayyeb

csscompressor/tests/base.py

@@ -8,8 +8,10 @@
 
 from csscompressor import compress
 
+import unittest
 
-class BaseTest:
+
+class BaseTest(unittest.TestCase):
  def _test(self, input, output):
  result = compress(input)
  if result != output.strip():