adds tests for crc

Makefile

@@ -0,0 +1,2 @@
+test:
+	python -m unittest discover

sgp30/__init__.py

@@ -1 +1,2 @@
 from .sgp30 import Sgp30
+from .crc import Crc8

tests/context.py

@@ -0,0 +1,7 @@
+# -*- coding: utf-8 -*-
+
+import sys
+import os
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+
+import sgp30

tests/test_crc.py

@@ -0,0 +1,10 @@
+from .context import sgp30
+
+import unittest
+class BasicTestSuite(unittest.TestCase):
+    """Basic test cases."""
+    def test_absolute_truth_and_meaning(self):
+        self.assertEqual(sgp30.Crc8().hash([0xBE, 0xEF]), 0x92,"testing doccumentation example")
+        self.assertEqual(sgp30.Crc8().hash([1,144]), 76, "First half of default reading")
+        self.assertEqual(sgp30.Crc8().hash([0,6]), 39, "second half of default reading, ")
+