Merge pull request ChartsOrg#1559 from danielgindi/codecov

Adds Codecov

.travis.yml

@@ -16,5 +16,5 @@ before_install:
 script:
   - bundle exec rake test
 
-# after_success:
-#   - bash <(curl -s https://codecov.io/bash)
+after_success:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,7 +1,7 @@
 **Version 3.0**, synced to [MPAndroidChart #1b9b3da](https://github.com/PhilJay/MPAndroidChart/commit/a233e38)
 
 ![alt tag](https://raw.github.com/danielgindi/Charts/master/Assets/feature_graphic.png)
-  ![Supported Platforms](https://img.shields.io/cocoapods/p/Charts.svg) [![Releases](https://img.shields.io/github/release/danielgindi/Charts.svg)](https://github.com/danielgindi/Charts/releases) [![Latest pod release](https://img.shields.io/cocoapods/v/Charts.svg)](http://cocoapods.org/pods/charts) [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage) [![Build Status](https://travis-ci.org/danielgindi/Charts.svg?branch=master)](https://travis-ci.org/danielgindi/Charts) 
+  ![Supported Platforms](https://img.shields.io/cocoapods/p/Charts.svg) [![Releases](https://img.shields.io/github/release/danielgindi/Charts.svg)](https://github.com/danielgindi/Charts/releases) [![Latest pod release](https://img.shields.io/cocoapods/v/Charts.svg)](http://cocoapods.org/pods/charts) [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage) [![Build Status](https://travis-ci.org/danielgindi/Charts.svg?branch=master)](https://travis-ci.org/danielgindi/Charts) [![codecov](https://codecov.io/gh/danielgindi/Charts/branch/master/graph/badge.svg)](https://codecov.io/gh/danielgindi/Charts)
 [![Join the chat at https://gitter.im/danielgindi/Charts](https://badges.gitter.im/danielgindi/Charts.svg)](https://gitter.im/danielgindi/Charts?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 ## Just a heads up: Charts 3.0 is **not** yet released to CocoaPods, as the version is not finalized yet.