Update README coverage badge

README.md

@@ -6,7 +6,7 @@ AiiDA (www.aiida.net) is a workflow manager for computational science with a str
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 |Latest release| [![PyPI version](https://badge.fury.io/py/aiida-core.svg)](https://badge.fury.io/py/aiida-core) [![conda-forge](https://img.shields.io/conda/vn/conda-forge/aiida-core.svg?style=flat)](https://anaconda.org/conda-forge/aiida-core) [![PyPI pyversions](https://img.shields.io/pypi/pyversions/aiida-core.svg)](https://pypi.python.org/pypi/aiida-core/) |
 |Getting help| [![Docs status](https://readthedocs.org/projects/aiida-core/badge)](http://aiida-core.readthedocs.io/) [![Google Group](https://img.shields.io/badge/-Google%20Group-lightgrey.svg)](https://groups.google.com/forum/#!forum/aiidausers)
-|Build status| [![Build Status](https://travis-ci.org/aiidateam/aiida-core.svg?branch=develop)](https://travis-ci.org/aiidateam/aiida-core) [![Coverage Status](https://coveralls.io/repos/github/aiidateam/aiida-core/badge.svg?branch=develop)](https://coveralls.io/github/aiidateam/aiida-core?branch=develop) |
+|Build status| [![Build Status](https://travis-ci.org/aiidateam/aiida-core.svg?branch=develop)](https://travis-ci.org/aiidateam/aiida-core) [![Coverage Status](https://codecov.io/gh/aiidateam/aiida-core/branch/develop/graph/badge.svg)](https://codecov.io/gh/aiidateam/aiida-core) |
 |Activity| [![PyPI-downloads](https://img.shields.io/pypi/dm/aiida-core.svg?style=flat)](https://pypistats.org/packages/aiida-core) [![Commit Activity](https://img.shields.io/github/commit-activity/m/aiidateam/aiida-core.svg)](https://github.com/aiidateam/aiida-core/pulse)