Support Codecov (#5)

* Support Codecov

* Remove coveralls

* Update ignore diretories

.eslintignore

@@ -1,4 +1,5 @@
 coverage/
+.nyc_output/
 
 demo/
 test/

.gitignore

@@ -3,3 +3,4 @@ npm-debug.log
 
 .nyc_output/
 coverage/
+coverage.lcov

README.md

@@ -4,7 +4,7 @@
 [![downloads count](https://img.shields.io/npm/dt/simple-data-table.svg)](https://www.npmjs.com/~piecioshka)
 [![travis](https://img.shields.io/travis/piecioshka/simple-data-table.svg?maxAge=2592000)](https://travis-ci.org/piecioshka/simple-data-table)
 [![dependencies](https://david-dm.org/piecioshka/simple-data-table.svg)](https://github.com/piecioshka/simple-data-table)
-[![coveralls](https://coveralls.io/repos/github/piecioshka/simple-data-table/badge.svg?branch=master)](https://coveralls.io/github/piecioshka/simple-data-table?branch=master)
+[![codecov](https://codecov.io/gh/piecioshka/simple-data-table/branch/master/graph/badge.svg)](https://codecov.io/gh/piecioshka/simple-data-table)
 
 :hammer: Lightweight and simple data table with no dependencies