Update Material Design Icons to 4.0.0

[lyleunderwood]

Closes #59

• Updates md script to reflect new structure introduced version 4.0.0 of https://github.com/google/material-design-icons
• Pulls in base style, outlined style, and twotone styles. There are also "round" and "sharp" styles, but I don't really know what those do. Should they also be included?
• Attempts to be backward-compatible. This adds the ic_ prefix that exists in 3.0.1 but not in 4.0.0 so that many icons are updated in place. I also have not removed any icons that no longer exist. A different strategy would be to do a major version bump and just clear out the md directory and rebuild it entirely.

[lyleunderwood]

Also, is this site building stuff from the README still accurate? I can't find a site directory anywhere, and it seems like there's a webpack config?

[wmira]

I believe this was moved here: https://github.com/wmira/react-icons-kit-site i need to confirm and test this before I publish

[wmira]

@lyleunderwood i updated the main site now with latest lib