Upgrade Webpack 3.0 for performance

[sculove]

Description

webpack 3.0 supports single scope hoisting.
if we apply it, we get the low file size and fast loading speed.

[netil]

• Ref: https://medium.com/webpack/webpack-3-official-release-15fd2dd8f07b#3750

[sculove]

we should be waiting for other libaray until update.

• webpack 3.0.0
• webpack-dev-server 2.5.0
• karma-webpack 2.0.3
• inject-loader 3.0.0

[netil]

1.0.1 dist files are built using webpack 3.0

• https://github.com/naver/billboard.js/tree/1.0.1/dist

Not changed the repo code due to webpack plugins compatibility with 3.0

[netil]

Take a look if is applicable.

• CommonJS Tree Shaker plugin for Webpack

[netil]

With greenkeeper integration, dependencies will be automatically updated.
Checkout #65 for the auto PR.

[sculove]

inject-loader is updated.