Add coveragerc

.coveragerc

+[run]
+source = km3io
+
+[report]
+include =
+    km3io/*
+omit =
+    tests/*
+exclude_lines =
+    pragma: no cover
+    raise AssertionError
+    raise NotImplementedError
+    if 0:
+    if __name__ == .__main__.:
+    if self.debug:
+    if settings.DEBUG