Extracted middleware to addons

For the purpose of other middleware injecting before/after named
middleware
Update broccoli-asset-rev.

Prevents deprecation warning.
Merge pull request #1450 from rwjblue/update-broccoli-asset-rev

Update broccoli-asset-rev.
Merge pull request #1446 from bcardarella/bc-middleware-addons

Extracted middleware to addons