Webpack 2 migration, package updates

[subhc]

Hi maintainers,

I have created this version with the following changes:

• Latest PF version - 3.23.3
• Project now uses webpack 2, various loader and plugins have also been updated, webpack config has been modified to work with webpack 2
• Deprecated autoprefixer-loader has been replaced with postcss-loader
• npm run clean now uses rimraf instead of rm, this makes the command platform independent

To accommodate these changes minor edits were necessary in the main.js and chart.js files. Let me know if there are any issues with this PR.

Thanks & Cheers, Subha