Upgrade all dev dependencies

[nstrelow]

With webpack and babel out of the way, the most signification dev dependencies have been updated.

Next all remaining should be updated, while checking the for breaking changes.

[nstrelow]

Dev dependecies for testing will be handle in #46 as we should also configure our testing.

[nstrelow]

Gulp had some breaking changes in 4.0.0.
We need to adapt our gulpfile to upgrade.
https://github.com/gulpjs/gulp/releases

[nstrelow]

Upgrading eslint packages will be handled in #47. There we will also make changes to the config.

[nstrelow]

Packages unsure if they are used or configured correctly:

• autoprefixer
• raw-loader
• url-loader