Drop travis build, switch to circle-ci (#2260)

* chore: drop travis build

* chore: send coverage from circle ci

.circleci/config.yml

@@ -17,13 +17,10 @@ jobs:
             echo "$(google-chrome --version)"
       - restore_cache:
           key: v1-npm-dependencies-{{ .Branch }}-{{ checksum "package.json" }}
-      - run:
-          name: Install dependencies
-          command: npm install
+      - run: npm install
       - save_cache:
           key: v1-npm-dependencies-{{ .Branch }}-{{ checksum "package.json" }}
           paths:
             - ./node_modules
-      - run:
-          name: Run Tests
-          command: npm run test
+      - run: npm test
+      - run: npm run codecov

.travis.yml

@@ -1,25 +0,0 @@
-language: node_js
-node_js:
-- 6
-dist: trusty
-sudo: false
-addons:
-  apt:
-    packages:
-      - google-chrome-stable
-
-before_script:
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start &
-  - sleep 3
-
-after_success:
-- npm run codecov
-
-notifications:
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/b90b361c0bc91a778bcc
-    on_success: change  # options: [always|never|change] default: always
-    on_failure: always  # options: [always|never|change] default: always
-    on_start: never     # options: [always|never|change] default: always

README.md

@@ -1,7 +1,6 @@
 # c3
 
-[![Build Status](https://travis-ci.org/c3js/c3.svg?branch=master)](https://travis-ci.org/c3js/c3)
-[![devDependency Status](https://david-dm.org/c3js/c3/dev-status.svg)](https://david-dm.org/c3js/c3#info=devDependencies)
+[![CircleCI](https://circleci.com/gh/c3js/c3.svg?style=svg)](https://circleci.com/gh/c3js/c3)
 [![license](http://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat)](https://github.com/c3js/c3/blob/master/LICENSE)
 [![codecov.io](https://codecov.io/github/c3js/c3/coverage.svg?branch=master)](https://codecov.io/github/c3js/c3?branch=master)
 [![Greenkeeper badge](https://badges.greenkeeper.io/c3js/c3.svg)](https://greenkeeper.io/)