Add configuration file for coverage and ignore the result file.

.coveragerc

+[run]
+source = topydo
+
+[report]
+exclude_lines =
+    pragma: no cover
+    def __repr__
+    raise AssertionError
+    raise NotImplementedError
+    if 0:
+    if __name__ == .__main__.:
+
+omit =
+    topydo/lib/ExitCommand.py
+    topydo/lib/Version.py

.gitignore

@@ -3,3 +3,4 @@
 build
 dist
 install
+.coverage