support webpack2 (#15)

* feat: support webpack 2

* refactor: share main loader options with other others

* refactor: add credit comment

* style: format

* test: turn on threadMode for concurrent testing with ava

* ci: upgrade node version on travis

* ci: use serial mode

* ci: use yarn to lock node_modules

* ci: add install command in .travis.yml

* ci: update .travis.yml

* ci: oops, it's circleci, not travis lol

* ci: bump ava version

* test: separate js and css snapshot

* test: separate test cases

* ci: store artifacts after running tests

* test: forgot applying extractTextPlugin for lang css

* fix #15

Author: fengzilong

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 npm-debug.log
 /__tests__/dist
+/demo