ADD coverage analysis

* branch coverage
* visualization with codecov.io
* added codecov-badge to README

.travis.yml

@@ -10,7 +10,7 @@ matrix:
   - python: 3.5
     env: TOXENV=py35
 before_install:
-    - pip install tox
-# command to run tests
+    - pip install tox codecov
 script:
     - tox
+    - codecov

README.rst

@@ -14,6 +14,10 @@ python-escpos - Python library to manipulate ESC/POS Printers
     :target: https://landscape.io/github/python-escpos/python-escpos/master
     :alt: Code Health
 
+.. image:: https://codecov.io/github/python-escpos/python-escpos/coverage.svg?branch=master
+    :target: https://codecov.io/github/python-escpos/python-escpos?branch=master
+    :alt: Code Coverage
+
 .. image:: https://readthedocs.org/projects/python-escpos/badge/?version=stable
     :target: http://python-escpos.readthedocs.org/en/latest/?badge=stable
     :alt: Documentation Status

tox.ini

@@ -4,5 +4,4 @@ envlist = py27, py34, py35
 [testenv]
 deps = nose
        coverage
-commands = nosetests
-# TODO: implement code coverage analysis (and of course tests at first)
+commands = nosetests --with-coverage --cover-erase --cover-branches