Bundle packr2 with the package

[Dids]

Since the packr2 utility is the primary culprit that increases the build time, it should we worth it if we bundle it with the application, or at the very least create a utility package that we can compile & run to do what we want.

Here's more documentation on bundling/embedding: https://godoc.org/github.com/gobuffalo/packr/v2/jam#Pack