add coverage and codecov

Author: bryanyang0528

Diff for: .coveragerc

@@ -0,0 +1,8 @@
+[run]
+branch = True
+source = ksql
+
+[report]
+include = 
+    ksql/*
+    tests/*

Diff for: .travis.yml

@@ -7,7 +7,10 @@ python:
   - "3.6"
 # command to install dependencies
 install:
-  - pip install nose vcrpy
+  - pip install nose vcrpy codecov coverage
   - pip install -r requirements.txt
 # command to run tests
-script: nosetests
+script: nosetests --with-coverage --cover-erase
+
+after_success:
+  - codecov