Separate images from JavaScript bundle.

[GirlBossRush]

This repo separates the inline images. The asset path is now user configurable, defaulting to versioned hosting via RawGit's production CDN.

Existing EmbedBox users upgrading will see an immediate file size drop without any configuration 😃. EmbedBox now sits at 40kb minified and gzipped! I believe a version bump to 2.0.0 is appropriate given this alters EmbedBox to include outside resources.

Cheers, Eric

• Replaces JPG assets with PNGs
• Fixes some legacy site CSS extract hacks.
• Adds asset archive creation to build step.

TODO

• [x] Test CDN in merged release.

Closes #124

[adamschwartz]

👍 great job.