Add test module for pytest.

.gitignore

+.cache
 *.pyc
 bin
 docs/_build

tests/module/test_parser.py

+from yangson.module.parser import Parser
+
+class TestParser:
+
+    text = """module test { // Nice module
+      prefix t;
+      namespace /* URI follows */ \t'http://example.com/test';
+      leaf foo {
+        type string;
+        default "hi \\"doc\\"";
+      }
+      leaf bar {
+        mandatory true;
+        type uint8;
+      }
+    }
+    """
+
+    def test_parser(self):
+        p = Parser(self.text)
+        s = p.parse_module()
+        ss = s.find_all("leaf")
+        sss1 = ss[0].find1("default")
+        sss2 = ss[1].find1("type", "uint8")
+        assert sss1.keyword == "default"