Adding coveralls integration

Run coverage with all tests and send results to coveralls.io.
diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..83429b0
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,7 @@
+[report]
+omit = */samples/*
+exclude_lines =
+    # Re-enable the standard pragma
+    pragma: NO COVER
+    # Ignore debug-only repr
+    def __repr__